Display body

ABSTRACT

A display body includes a display surface including a plurality of display region groups. Each display region includes at least one reflection surface that is configured to reflect light incident on the display surface toward an area including a corresponding one of reflection directions that are associated with the respective display region groups. Each display region group is configured to form an image unique to the display region group in a corresponding one of the reflection directions through reflection of light on the reflection surfaces in the display region group. The display region groups are configured to form, in two adjacent ones of the reflection directions, different images that have a interrelation between each other.

CROSS-REFERENCE

Priority is claimed on Japanese Patent Application Nos. 2016-145599,filed Jul. 25, 2016 and 2017-048905, filed on Mar. 14, 2017. The presentapplication is a continuation application of International ApplicationPCT/JP2017/026885, filed on Jul. 25, 2017. The contents of the aboveapplications are incorporated herein in their entirety, including thespecification and the drawings.

BACKGROUND

The present disclosure relates to a display body that displays an imagethrough reflection of light.

Various objects such as certification documents, securities, banknotesare required to be counterfeit-resistant. Techniques to increasedifficulty in counterfeiting an object include attaching acounterfeit-resistant display body to the object.

For example, Japanese Laid-Open Patent Publication No. 2004-85681describes a display body that records a latent image of a meaningfulshape, such as a character, by using a diffraction grating that producesdiffracted light in a reflection direction oblique to the displaysurface. The latent image recorded by the diffraction grating isdifficult to perceive when viewed in the direction of the normal to thedisplay surface. However, the latent image recorded by the diffractiongrating is clearly perceived when the display surface is viewed alongthe reflection direction.

However, the display body of Patent Document 1 merely displays thelatent image, which is recorded by the diffraction grating, when thedisplay surface is viewed along a reflection direction. In recent years,various objects are sought to have aesthetic appearances, and there is ahigh demand for display bodies with improved aesthetic appearance.

SUMMARY

To address this need, it is an objective of the present disclosure toprovide a display body with an improved aesthetic appearance.

To achieve the foregoing objective, a display body is provided thatincludes a display surface including a plurality of display regiongroups, each including a plurality of display regions. Each displayregion includes at least one reflection surface that is configured toreflect light incident on the display surface toward an area including acorresponding one of reflection directions that are associated with therespective display region groups. Each display region group isconfigured to form an image unique to the display region group in acorresponding one of the reflection directions through reflection oflight on the reflection surfaces in the display region group. Thedisplay region groups are configured to form, in two adjacent ones ofthe reflection directions, different images that have a interrelationbetween each other.

With this configuration, when the observation direction is shifted,different images having a interrelation between each other areperceived. This improves the aesthetic appearance of the display body.

In the above-described configuration, the images having theinterrelation may each include an element image, and the element imagesare identical in type and different from each other in at least one ofposition of the element images, shape of the element images, size of theelement images, light and dark of the element images, and shade of theelement images.

This configuration allows the interrelation between the images to beeasily recognized by the observer when the observation direction ischanged. This increases the advantage of displaying images that haveinterrelated but different contents according to the reflectiondirections.

In the above-described configuration, the interrelation may includecontinuous variations, along a sequence of the reflection directions, inat least one of position of the element images, shape of the elementimages, light and dark of the element images, size of the elementimages, and shade of the element images in the images.

This configuration continuously varies the content of the image when thereflection direction varies continuously. This further improves theaesthetic appearance of the display body.

In the above-described configuration, the two adjacent reflectiondirections may be a first reflection direction and a second reflectiondirection. The plurality of display region groups may include a firstdisplay region group configured to form an image in the first reflectiondirection, and a second display region group configured to form an imagein the second reflection direction. The display regions of the firstdisplay region group may be adjacent to the display regions of thesecond display region group.

In this configuration, the display regions for displaying the imageshaving the interrelation are adjacent to each other, allowing thereflection surfaces adjacent to each other to have similar structures.This reduces the load required to manufacture the display body.

In the above-described configuration, the plurality of reflectionsurfaces may include reflection surfaces that form different angles withthe display surface and reflection surfaces having differentorientations.

This configuration includes reflection surfaces that form differentangles with the display surface and reflection surfaces having differentorientations. This facilitates establishing an association between adisplay region group and an intended reflection direction.

The above-described configuration may include a plurality of pixelslocated on the display surface. Each display region may be one of thepixels.

This configuration allows the structure of the display regions to bedesigned based on a raster image, which is an image formed by acollection of pixels.

The above-described configuration may include a substrate and areflection layer covering the substrate. The reflection layer mayinclude the reflection surfaces of the display regions.

This configuration can make the intensity of the reflected lighttraveling in the reflection direction different from that of the lightreflected by the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing unit cells of a display body of a firstembodiment.

FIG. 2 is a perspective view showing a pixel of the first embodiment.

FIGS. 3A to 3D are perspective views showing the structures of pixelsassociated with different tones in the image to be displayed.

FIGS. 4A to 4D are cross-sectional views showing the cross-sectionalstructures of the pixels shown in FIGS. 3A to 3D.

FIGS. 5A to 5D are diagrams for illustrating the operations of thepixels shown in FIGS. 3A to 3D.

FIGS. 6A to 6C are diagrams each illustrating an example of a method fordynamically displaying an image with a display body of a modification ofthe first embodiment.

FIG. 7 is a diagram for illustrating the azimuth angle of a display bodyof a modification of the first embodiment.

FIGS. 8A to 8D are diagrams each showing an example of a reflectionsurface of a display body of a modification of the first embodiment.

FIGS. 9A to 9C are perspective views each showing the structure of apixel having a plurality of reflection sections in the display body.

FIG. 10A is a cross-sectional view showing the cross-sectional structuretaken along line I-I in FIG. 9A.

FIG. 10B is a cross-sectional view showing the cross-sectional structuretaken along line II-II in FIG. 9B.

FIG. 10C is a cross-sectional view showing the cross-sectional structuretaken along line III-III in FIG. 9C.

FIGS. 11A to 11C are diagrams of spectrums showing intensitydistributions of diffracted light in diffraction images.

FIG. 12 is a cross-sectional view showing the cross-sectional structureof a display body of a modification of the first embodiment.

FIG. 13 is a ray diagram showing the light incident on a display body ofa modification of the first embodiment and the light emerged from thedisplay body.

FIG. 14A is a diagram showing the normal direction in a state where adisplay body of a modification of the first embodiment is observed fromthe first observation side.

FIG. 14B is a diagram showing the normal direction in a state where thedisplay body of the modification of the first embodiment is observedfrom the second observation side.

FIG. 15 is a plan view showing the planar structure of a display body ofa modification of the first embodiment.

FIGS. 16A and 16B are diagrams for illustrating the operation of thedisplay body of the modification of the first embodiment.

FIG. 17 is a plan view showing the planar structure of a display body ofa modification of the first embodiment.

FIG. 18 is a ray diagram showing the light incident on a display body ofa modification of the first embodiment and the light emerged from thedisplay body.

FIG. 19 is a schematic view showing the configuration of unit cells of adisplay body of a second embodiment.

FIG. 20 is a diagram for illustrating an example of a method fordynamically displaying an image with the display body of the secondembodiment.

FIGS. 21A to 21C are diagrams each illustrating an example of a methodfor dynamically displaying an image with a display body of amodification of the second embodiment.

FIG. 22 is a schematic view showing the configuration of unit cells of adisplay body of a third embodiment.

FIG. 23 is a diagram for illustrating an example of a method fordynamically displaying an image with the display body of the thirdembodiment.

FIG. 24A is a diagram for illustrating an example of a method fordynamically displaying an image with a display body of a modification ofthe third embodiment.

FIG. 24B is a schematic view showing the configuration of unit cells ofa display body of a modification of the third embodiment.

FIG. 24C is a diagram for illustrating an example of a method fordynamically displaying an image with the display body shown in FIG. 24B.

FIGS. 25A to 25C are diagrams for illustrating an example of a methodfor dynamically displaying an image with a display body of a fourthembodiment.

FIG. 26 is a schematic view showing a display body of a modification ofthe fourth embodiment and an image displayed by the display body.

FIG. 27 is a diagram for illustrating a zenith angle formed by the Zdirection and the normal direction to a surface forming the imagedisplayed by the display body of a modification of the fourthembodiment.

FIG. 28 is a schematic view showing the configuration of unit cells of adisplay body of a fifth embodiment.

FIG. 29 is a diagram showing an ellipse used to set the sizes of pixelregions in the display body of the fifth embodiment.

FIGS. 30A to 30D are perspective views showing the structures of pixels,which are associated with tones in the image to be displayed, in adisplay body of another embodiment.

FIGS. 31A to 31D are cross-sectional views showing the cross-sectionalstructures of the pixels shown in FIGS. 30A to 30D.

FIGS. 32A to 32D are perspective views showing the structures of pixels,which are associated with tones in the image to be displayed, in adisplay body of another embodiment.

FIGS. 33A to 33D are cross-sectional views showing the cross-sectionalstructures of the pixels shown in FIGS. 32A to 32D.

FIGS. 34A and 34B are diagrams for illustrating the operation of adisplay body of another embodiment.

FIGS. 35A and 35B are diagrams for illustrating the operation of adisplay body of another embodiment.

FIGS. 36A and 36B are perspective views showing the structures of pixelsof other embodiments.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A display body according to a first embodiment will now be describedwith reference to FIGS. 1 to 5.

The image displayed by the display body is not limited to a raster imagecomposed of repeated pixels, which is an example of display regions, andmay be a vector image composed of a collection of display regionsrepresented by vectors. For convenience of explanation, the followingdescription on a display body uses a pixel as an example of a displayregion and uses a collection of pixels for displaying an image in asingle reflection direction as an example of a display pixel group. Theaccompanying drawings are not necessarily to same scale or aspect ratioas actual and may include enlarged views of characteristic parts of thedisplay body in order to clearly show its features.

As shown in FIG. 1, a display body 10 includes a display surface 10S, onwhich a plurality of pixels 11A is arranged. Each pixel 11A is a minimumunit in the structure for displaying an image P in the reflectiondirection. Pixels 11A are repeated to form an independent image. Pixels11A are display regions, which are typically arranged in a matrix on thedisplay surface 10S. The image P may be a character, a graphics, asymbol, or an illustration, for example. The image P of the presentembodiment is circular. The display surface 10S may be flat or curved.

The display surface 10S includes a plurality of unit cells L1E, eachhaving a predetermined size that occupies a predetermined area. The unitcells L1E may be arranged in a matrix on the display surface 10S. A unitcell L1E is a minimum unit that is repeated on the display surface 10Sto provide optical effects. In the example shown in FIG. 1, the pixels11A are arranged in the unidirectional X direction, and in theunidirectional Y direction which is perpendicular to the X direction.Each unit cell L1E of the rectangular grid includes one pixel 11A.

Further, the display surface 10S of the present embodiment includes aplurality of pixel groups 11Sa to 11Sd, each associated with acorresponding one of different tones in the image to be displayed. Inthe example shown in FIG. 1, a circular first pixel group 11Sa islocated at the center of the image P. An annular second pixel group 11Sbis located next to and radially outward of the first pixel group 11Sa.An annular third pixel group 11Sc is located next to and radiallyoutward of the second pixel group 11Sb. An annular fourth pixel group11Sd is located next to and radially outward of the third pixel group11Sc. The pixel groups 11Sa to 11Sd each includes a plurality of unitcells L1E. In each of the pixel groups 11Sa to 11Sd, the unit cells L1Einclude the identical pixels 11A.

As shown in FIG. 2, a pixel 11A includes a reflection surface 11S whichreflects the light incident on the display surface 10S toward an areaincluding the reflection direction associated with the each of the pixelgroups 11Sa to 11Sd. The reflection surface 11S is an optical surfaceintersecting with the display surface 10S. The reflection surface 11Sand the display surface 10S form an inclination angle θ, which isuniform along the Y direction. Each reflection surface 11S is shaped soas to reflect the light that is incident on the reflection surface 11Sat an incident angle in a given range. Each reflection surface 11S isalso shaped such that its reflection angle corresponds to the reflectiondirection that is common to the pixel group. The reflection surface 11Sis a specular surface, which specularly reflects visible light. Thelight that is incident on the reflection surface 11S from a givendirection is regularly reflected in a direction corresponding to theinclination angle θ of the reflection surface 11S. Each of the pixelgroups 11Sa to 11Sd forms an image unique to the pixel group in thereflection direction associated with the pixel group through reflectionat the reflection surfaces 11S of the pixel group.

In two adjacent reflection directions among the plurality of reflectiondirections, different images are formed that have a interrelationbetween each other. Two adjacent reflection directions are reflectiondirections that have the minimum difference between each other among thevarious reflection directions unique to the respective display regiongroups. Images that have an interrelation include the same type ofelement images, but these element images differ from each other inshape. The shapes of the element images vary along the sequence ofreflection directions with regularity. In other words, the shapes varycontinuously. In the example shown in FIG. 1, the optical effects of thepixels 11A forming the pixel groups 11Sa to 11Sd display a dynamic imageP, which expands radially outward from the radial center of the image Pin a continuous manner as the reflection direction of the display body10 varies. In the image P, the element images have annular shapes, whichare geometrical patterns.

Each pixel 11A preferably has a structure width of 1 μm to 300 μm. Astructure width of 1 μm or more limits generation of diffracted light,which produces iridescent color in the image. A structure width of 300μm or less reduces the likelihood that the observer perceives theinclined structure of the reflection surface 11S of each pixel 11A andlimits decrease in the resolution of the image P displayed by thedisplay body 10. The structure width is the width of the pixel 11A inthe direction in which a plurality of pixels 11A is arranged in each ofthe pixel groups 11Sa to 11Sd.

The pixels 11A may be made of any material. Examples of the material ofthe pixels 11A include a polymer composition. In addition to a polymercomposition, the material of the pixels 11A may contain materials suchas a curing agent, a plasticizer, a dispersant, various leveling agents,an ultraviolet absorber, an antioxidant, a viscosity modifier, alubricant, and a photostabilizer. Each pixel 11A may be a projectionforming a triangular prism on the display surface 10S, or may be adepression having a reflection surface 11S in the display surface 10S.

The configuration of the reflection surface 11S of each pixel 11A is nowdescribed in detail. The traveling direction of the light reflected bythe reflection surface 11S may be the direction in which light isdiffracted by the reflection surface 11S or may be different from thedirection of light diffracted by the reflection surface 11S.

As shown in FIGS. 3A to 3D, pixels 11A are set at different rotationalpositions about the axis perpendicular to the display surface 10S, sothat the reflection surfaces 11S have mutually different orientations.With respect to the pixel 11A shown in FIG. 3A, the pixels 11A of FIGS.3B to 3D are arranged in ascending order of difference in rotationangles.

FIGS. 4A to 4D are cross-sectional views of the pixels 11A of FIGS. 3Ato 3D in the X direction. That is, FIG. 4A shows the cross-sectionalview of the pixel 11A of FIG. 3A, FIG. 4B shows the cross-sectional viewof the pixel 11A of FIG. 3B, FIG. 4C shows the cross-sectional view ofthe pixel 11A of FIG. 3C, and FIG. 4D shows the cross-sectionalstructure of the pixel 11A of FIG. 3D. As shown in FIG. 4A, theinclination angle formed by the reflection surface 11S and the displaysurface 10S of the reference pixel 11A is θ1. As shown in FIG. 4B, theinclination angle formed by the reflection surface 11S and the displaysurface 10S of the pixel 11A that differs from the reference pixel 11Ain rotation angle is θ2.

As shown in FIGS. 4A and 4B, when the orientation of the reflectionsurface 11S of a pixel 11A is aligned with the X direction, the lengthof the oblique side of the reflection surface 11S of this pixel 11A is adistance L1. In contrast, when the orientation of the reflection surface11S of a pixel 11A is aligned with a direction that intersects with theX direction, the length of the oblique side of the reflection surface11S of this pixel 11A is a distance L2, which is longer than distanceL1. The reflection surfaces 11S of pixels 11A have the equal height H,regardless of the orientations of the reflection surfaces 11S of thepixels 11A. Thus, as shown in FIG. 4B, the inclination angle θ2 formedby the reflection surface 11S of the pixel 11A that differs from thereference pixel 11A in rotation angle is smaller than the inclinationangle θ1 of the reflection surface 11S of the reference pixel 11A shownin FIG. 4A.

Further, as shown in FIG. 4C, when the reflection surface 11S of a pixel11A differs more greatly in orientation from the reference pixel 11Athan the pixel 11A shown in FIG. 4B, the length of the oblique side ofthe reflection surface 11S of this pixel 11A is a distance L3, which islonger than the distance L2. The reflection surfaces 11S of pixels 11Ahave the equal height H, regardless of the orientations of thereflection surfaces 11S of the pixels 11A. Thus, as shown in FIG. 4C,the inclination angle θ3 formed by the reflection surface 11S of thepixel 11A that has a greater difference in rotation angle from thereference pixel 11A is smaller than the inclination angle θ2 of thereflection surface 11S of the pixel 11A in FIG. 4B, which have a smallerdifference in rotation angle from the reference pixel 11A.

Further, as shown in FIG. 4D, when the reflection surface 11S of a pixel11A differs more greatly in orientation from the reference pixel 11Athan the pixel 11A shown in FIG. 4C, the length of the oblique side ofthe reflection surface 11S of this pixel 11A is a distance L4, which islonger than the distance L3. The reflection surfaces 11S of pixels 11Ahave the equal height H, regardless of the orientations of thereflection surfaces 11S of the pixels 11A. Thus, as shown in 4D, theinclination angle θ4 formed by the reflection surface 11S of the pixel11A that have a greater difference in rotation angle from the referencepixel 11A is smaller than the inclination angle θ3 of the reflectionsurface 11S of the pixel 11A shown in FIG. 4C, which have a smallerdifference in rotation angle from the reference pixel 11A.

That is, there is a certain interrelation between the orientation of thereflection surface 11S of a pixel 11A and the inclination angle θ (θ1 toθ4) of the reflection surface 11S of the pixel 11A in a cross sectionperpendicular to the display surface 10S. Different orientations of thereflection surfaces 11S of pixels 11A result in different inclinationangles θ (θ1 to θ4) of the reflection surfaces 11S of the pixels 11A inthe cross sections. The reflection surface 11S of each pixel 11A may bea flat or non-flat surface having an inclination angle θ. A non-flatreflection surface 11S may be a surface including minute projections anddepressions or may be a curved surface. The inclination angle θ of anon-flat reflection surface 11S may be the inclination angle of a flatreference surface that approximates the non-flat reflection surface 11S.

As shown in FIGS. 5A to 5D, the inclination angle θ (θ1 to θ4) of thereflection surface 11S of each pixel 11A may be set such that thetraveling direction of the light reflected by the reflection surface 11Sdiffers from or coincides with the direction of light diffracted by thereflection surface 11S. For example, the inclination angle θ may besized such that the traveling direction of the light specularlyreflected by the reflection surface 11S coincides with the travelingdirection of m-th order diffracted light (m is an integer of 1 or more),which is produced by the reflection surface 11S and has a specificwavelength A. In this case, the m-th order diffracted light travels inthe reflection direction DK.

Specifically, an incident angle α is formed by the traveling directionof the incident light on the reflection surface 11S and the direction ofthe normal to the display surface 10S. A diffraction angle β (β1, β2, β3or β4) is formed by the traveling direction of the m-th order diffractedlight and the direction normal to the display surface 10S. Thediffracted light produced by the pixel 11A has a certain wavelength λ,and the diffraction angle β is a value unique to the inclination angle θof the reflection surface 11S. Incident angle α, diffraction angle β,wavelength λ, and inclination angle θ satisfy Equations (1) and (2)below.sin α+sin β=mλ(m is an integer of 1 or more)  (1)θ=(α−β)/2  (2)

The reflection surface 11S having the inclination angle θ describedabove diffracts the m-th order diffracted light of a certain wavelengthλ with high diffraction efficiency. For example, a reflection surface11S converts white incident light into colored light in the reflectiondirection with high conversion efficiency. In addition, since each pixel11A has one reflection surface 11S, the image displayed in thereflection direction DK can be high resolution. As a result, the imagedisplayed in the reflection direction DK is formed by the lightdiffracted with high diffraction efficiency and therefore has increasedvisibility.

When light beams are incident from a given direction and at the sameincident angle α onto reflection surfaces 11S of pixels 11A havingdifferent inclination angles θ, the light beams are diffracted indifferent reflection directions DK.

Specifically, the diffraction angle β is obtained using Equation (2)based on the inclination angle θ of the reflection surface 11S of thepixel 11A and the incident angle α.β=α−2θ  (3)

As is apparent from Equation (3), assuming that the incident angle α isfixed, when the reflection surface 11S of a pixel 11A has theinclination angle θ1, which is a relatively large angle, the diffractionangle β is relatively small. Accordingly, as shown in FIGS. 5A and 5B,the diffraction angle β2 that results when the reflection surface 11S ofa pixel 11A has the inclination angle θ2, which is a relatively smallangle, is larger than the diffraction angle β1 that results when theinclination angle θ of the reflection surface 11S of a pixel 11A is θ1,which is a relatively large angle.

Similarly, as shown in FIGS. 5B and 5C, the diffraction angle β3 thatresults when the reflection surface 11S of a pixel 11A has theinclination angle θ3, which is a relatively small angle, is larger thanthe diffraction angle β2 that results when the inclination angle θ ofthe reflection surface 11S of a pixel 11A is θ2, which is a relativelylarge angle. Furthermore, as shown in FIGS. 5C and 5D, the diffractionangle β4 that results when the reflection surface 11S of a pixel 11A hasthe inclination angle θ4, which is a relatively small angle, is largerthan the diffraction angle β3 that results when the inclination angle θof the reflection surface 11S of a pixel 11A is 63, which is arelatively large angle.

That is, there is a certain interrelation between the inclination angleθ of the reflection surface 11S of a pixel 11A and the diffraction angleβ. Changing the inclination angle θ of the reflection surface 11S of apixel 11A changes the direction in which an image is displayed by thelight diffracted by the pixel 11A, in other words, the reflectiondirection.

In the present embodiment, the pixel 11A shown FIG. 5A is used for thefirst pixel group 11Sa of the pixels 11A forming the image P shown inFIG. 1. The pixel 11A shown in FIG. 5B is used for the second pixelgroup 11Sb. The pixel 11A shown in FIG. 5C is used for the third pixelgroup 11Sc. The pixel 11A shown in FIG. 5D is used for the fourth pixelgroup 11Sd.

When the display body 10 is observed from the direction corresponding tothe diffraction angle β1, the image displayed by the pixels 11A shown inFIG. 5A, which is the image displayed by the circular pixel group 11Sain the image P of FIG. 1, is perceived with high brightness. When thedisplay body 10 is observed from the direction corresponding to thediffraction angle β2, the image displayed by the pixels shown in FIG.5B, which is the image displayed by the annular pixel group 11Sb, isperceived with high brightness.

When the display body 10 is observed from the direction corresponding tothe diffraction angle β3, the image displayed by the pixels 11A shown inFIG. 5C, which is the image displayed by the annular pixel group 11Sc,is perceived with high brightness. When the display body 10 is observedfrom the direction corresponding to the diffraction angle β4, the imagedisplayed by the pixels 11A shown in FIG. 5D, which is the imagedisplayed by the annular pixel group 11Sd, is perceived with highbrightness.

That is, as the reflection direction of the display body 10 iscontinuously varied from the direction corresponding to the diffractionangle β1 toward the direction corresponding to the diffraction angle β4,the image P shown in FIG. 1 is perceived as a dynamic image thatcontinuously expands radially outward from the radial center of theimage P.

The combination of the pixels 11A corresponding to the diffraction angleβ1 and the pixels 11A corresponding to the diffraction angle β2 is acombination of sets of pixels 11A for displaying images in adjacentdirections, in other words, a combination of sets of pixels 11Aassociated with adjacent reflection directions. These sets of pixels 11Aare adjacent to each other on the display surface 10S. As for thecombination of the pixels 11A corresponding to the diffraction angle β2and the pixels 11A corresponding to the diffraction angle β3, these setsof pixels 11A are adjacent to each other on the display surface 10S. Asfor the combination of the pixels 11A corresponding to the diffractionangle β3 and the pixels 11A corresponding to the diffraction angle β4,these sets of pixels 11A are adjacent to each other on the displaysurface 10S. That is, when two adjacent reflection directions among aplurality of reflection directions are referred to as a first reflectiondirection and a second reflection direction, the pixels 11A forming thepixel group that displays an image in the first reflection direction areadjacent to the pixels 11A forming the pixel group that displays animage in the second reflection direction.

This structure provides the visual effect that defines the direction ofthe sequence of movements in the image P. Accordingly, when thedirection in which the display body 10 is observed is continuouslyvaried, the image P moves radially outward from its radial center alongthe adjacent regions in the image P.

This visual effect of defining the direction of sequence of imagemovements is achieved by the inclination angles θ of the reflectionsurfaces 11S, which have a certain interrelation among the pixels 11Aand vary sequentially with predetermined regularity. This visual effectof defining the direction of sequence of image movements is alsoachievable by a configuration in which the traveling direction of thelight reflected by the reflection surface 11S differs from the directionof light diffracted by the reflection surface 11S.

Examples of a method for manufacturing the display body 10 includeduplicating the display body 10 from an original plate. To manufacturethe original plate, a photosensitive resin is applied to one surface ofa planar substrate and then irradiated with a beam, so that a part ofthe photosensitive resin is exposed and developed. Then, a metal stamperis produced from the original plate by electroplating, for example, andthe display body 10 is duplicated using this metal stamper as thematrix. The metal stamper may be manufactured by cutting a metalsubstrate using lathe technique. The display body 10 may be duplicatedby forming a shaped product using a technique such as a heat embossingmethod, a casting method, or a photopolymer method, and byvapor-depositing a reflection layer on the surface of the shapedproduct.

The photopolymer method introduces a radiation-curing resin into the gapbetween a flat substrate, such as a plastic film, and the metal stamper,cures the radiation-curing resin by radiation, and removes the curedresin layer from the metal stamper together with the substrate. Thephotopolymer method produces pixels 11A with high structural accuracy,heat resistance, and chemical resistance and is thus more desirable thana pressing method and a casting method, which use a thermosetting resin.

The reflection layer may be made of any material that has reflectivityand can form a reflection layer through vapor deposition. The reflectionfilm may be made of a metal or an alloy. The reflection film may be madeof a metal, such as aluminum, gold, silver, platinum, nickel, tin,chromium, or zirconium, or alloys thereof. The reflection layer mayinclude a layer made of a highly refractive material, such as zinc oxideand zinc sulfide. Aluminum and silver are preferable over othermaterials since they have particularly high reflectivities for thevisible light region.

The method for forming the reflection layer is not limited to the vapordeposition, and any method may be used that can form a reflection layeron the reflection surface 11S of the pixel 11A. The reflection layer maybe formed by a physical vapor deposition method (PVD method) or achemical vapor deposition method (CVD method). The physical vapordeposition method (PVD method) may be (a) a vacuum deposition method, asputtering method, an ion plating method, or an ion cluster beam method.The chemical vapor deposition method (CVD method) may be (b) a plasmachemical vapor deposition method, a thermal chemical vapor depositionmethod, or a photochemical vapor deposition method. However, of thesemethods, the vacuum evaporation method and the ion plating method arepreferable over the others. These methods have higher productivity andproduce desirable reflection layers.

As described above, the first embodiment has the following advantages.

(1) When the direction in which the display body 10 is observedisshifted, images that have interrelated but different contents aredisplayed in turn in different observation directions. This increasesthe aesthetic appearance of the display body 10.

(2) While the direction in which the display body 10 is observed isshifted, the variations in the image P are perceived in a wide viewingzone. This allows for easier, quick authentication of the display body10 based on the image P.

(3) Images having an interrelation include the same type of elementimages, but differ in shape of the element images. The interrelationbetween the images is thus easily recognized by the observer when theobservation direction is changed. This enhances the effect of displayingimages that have interrelated but different contents according to thereflection direction.

(4) When the direction in which the display body 10 is observed isshifted continuously, the image P continuously varies in content. Thisfurther increases the aesthetic appearance of the display body 10.

(5) The pixel groups 11Sa to 11Sd, which provide continuous varies ofcontent in the image P, are adjacent to one another, such that adjacentreflection surfaces 11S may be similar in structure. This reduces theload required to manufacture the display body 10.

(6) There is a certain interrelation between the orientation of thereflection surface 11S of each pixel 11A and the direction in which thereflection surface 11S reflects light. The orientation of the reflectionsurface 11S of each pixel 11A may be used as a control parameter inadjusting the direction of light reflected by the pixel 11A having thereflection surface 11S. This facilitates establishing an associationbetween an intended reflection direction and each of the pixel groups11Sa to 11Sd, each formed by a collection of pixels 11A.

(7) The display surface 10S includes a plurality of pixels 11A, and eachof the unit cells of the display surface 10S contains one pixel 11A. Assuch, it is possible to design the structure of the pixels 11A in unitcells based on a raster image, which is an image formed by a collectionof small color points, or dots.

(8) The reflection surface 11S of each pixel 11A is in the reflectionlayer covering the substrate. This can make the reflected lighttraveling in the reflection direction different in intensity from thatof the reflected light reflected by the substrate.

The first embodiment described above may be modified as follows.

The method for dynamically displaying an image of a geometric patternwhen the direction in which the display body 10 is observed iscontinuously varied may be modified as the modifications describedbelow.

As shown in FIG. 6A, the configuration of the first example displays adynamic image P that expands linearly and radially from the center ofthe display surface 10S in a plan view of the display surface 10S. Theimage P expands in accordance with varies in reflection directions ofthe display region groups. In this example, in a plan view of thedisplay surface 10S, the first pixel group 11Sa, the second pixel group11Sb, the third pixel group 11Sc, and the fourth pixel group 11Sd arearranged in this order from the center of the display surface 10S towardthe outer side in the radial direction. The orientations of thereflection surfaces 11S of the pixels 11A gradually vary in the radialdirection from the center of the display surface 10S, so that the imagedescribed above is displayed.

As shown in FIG. 6B, the configuration of the second example displays adynamic image P that expands spirally and radially from the center ofthe display surface 10S in a plan view of the display surface 10S. Theimage P expands in accordance with varies in reflection directions ofthe display region groups. In a plan view of the display surface 10S,the first pixel group 11Sa, the second pixel group 11Sb, the third pixelgroup 11Sc, and the fourth pixel group 11Sd are arranged in this orderfrom the center of the display surface 10S toward the outer side in theradial direction. The orientations of the reflection surfaces 11S of thepixels 11A gradually vary in the radial direction from the center of thedisplay surface 10S, so that the image described above is displayed.

As shown in FIG. 6C, the configuration of the third example displays adynamic image P that is wave-shaped and moves continuously from theupper side to the lower side in a plan view of the display surface 10Sas viewed in the figure. The image P moves in accordance with varies inreflection directions of the display region groups. In this example, thepixel groups each extend in a wave-shaped line in the lateral directionas viewed in the figure. The pixel groups are arranged in the verticaldirection, which is perpendicular to the lateral direction. The firstpixel group 11Sa, the second pixel group 11Sb, the third pixel group11Sc, and the fourth pixel group 11Sd are arranged in this order fromthe upper side to the lower side of the display surface 10S as viewed inthe figure. The orientations of the reflection surfaces 11S of thepixels 11A vary gradually in the direction from the upper side to thelower side of the display surface 10S as viewed in the figure, so thatthe image described above is displayed.

In the examples described above referring to FIGS. 3A to 3D, forconvenience of description, the orientations of the reflection surfaces11S of the pixels 11A vary such that their angles are within the rangethat allows the reflection surfaces 11S of the pixels 11A to have thesame height H in cross sections perpendicular to the display surface10S. However, as long as the inclination angles θ of the reflectionsurfaces 11 vary with the orientations of the reflection surfaces 11S,the orientations of the reflection surfaces 11S may be adjusted using arange of angles that causes variation in the heights H of the reflectionsurfaces 11S of the pixels 11A in cross sections perpendicular to thedisplay surface 10S. That is, any range of angles may be used providedthat there is a certain interrelation between the orientation of thereflection surfaces 11S of a pixel 11A and the inclination angle θ ofthe reflection surface 11S of the pixel 11A in a cross sectionperpendicular to the display surfaces 10S, and that varying theorientation of the reflection surface 11S of a pixel 11A varies theinclination angle θ of the reflection surface 11S of the pixel 11A inthe cross section. The visual effect of defining the direction ofsequence of image movements can also be achieved by a configuration thatincludes multiple display region groups that are identical inorientation of the reflection surfaces 11S, as long as these displayregion groups have mutually different inclination angles θ.

The orientation of the reflection surface 11S of each pixel 11A may bedefined as follows. In the following description, the directionperpendicular to the XY plane is the Z direction.

As shown in FIG. 7, an azimuth angle Φ is formed between a projectiondirection DP, which is the projection normal to the reflection surface11S onto the display surface 10S, and one direction along the displaysurface 10S, for example the Y direction. When the projection directionDP coincides with the Y direction, the azimuth angle Φ of the reflectionsurface 11S is 0°. The orientation of the reflection surface 11S can beidentified from the azimuth angle Φ. The range of the azimuth angle Φ isexpressed by Expression (4).0°≤Φ<360°  (4)

The pixel 11A does not have to be a projection forming a triangularprism on the display surface 10S. The pixel 11A may be a projection withthe following shapes. In FIGS. 8A to 8D, for the sake of convenience ofillustrating the variation in height of a pixel 11A using a plane, theheights are expressed as gradations of lightness such that a position inthe pixel 11A that has a greater height in the Z direction has a lowerlightness.

That is, when the azimuth angle Φ is 0° as shown in FIG. 8A or 90° asshown in FIG. 8D, one pixel 11A may occupy the entire unit cell L1E.

In contrast, when the azimuth angle Φ is 30° as shown in FIG. 8B or 60°as shown in FIG. 8C and the area that is occupied by reflection sectionsin a unit cell L1E as viewed in the Z direction is maximized, one pixel11A may include a plurality of reflection sections. That is, a unit cellL1E may include a first reflection section 11A1 and a second reflectionsection 11A2, which occupies the area that is free of the firstreflection section 11A1. The second reflection section 11A2 has areflection surface 11S, which has the same azimuth angle Φ and the sameinclination angle θ as the first reflection section 11A1. In otherwords, one unit cell L1E may contain two reflection sections.

In addition to when the first and second reflection sections 11A1 and11A2 have an azimuth angle Φ of 30° or 60°, the unit cell L1E maycontain two reflection sections when the first and second reflectionsections 11A1 and 11A2 have an azimuth angle Φ of other than 0°, 90°,180°, and 270°.

As described with reference to FIGS. 8B and 8C, one unit cell L1E maycontain two or more reflection sections. For example, as described belowreferring to FIGS. 9A to 10C, one unit cell L1E may contain threereflection sections. That is, in one unit cell L1E, one pixel mayinclude a plurality of reflection sections.

FIGS. 9A to 9C each show the structure of a pixel including two or morereflection sections in one unit cell L1E. FIGS. 10A to 10C showcross-sectional structures of the reflection sections shown in FIGS. 9Ato 9C. Specifically, FIG. 10A shows the cross-sectional structure of thereflection sections of FIG. 9A, FIG. 10B shows the cross-sectionalstructure of the reflection sections of FIG. 9B, and FIG. 10C shows thecross-sectional structure of the reflection sections of FIG. 9C. Thefollowing descriptions on reflection sections in one unit cell L1E aregiven referring to the perspective views of FIGS. 9A to 9C and thecross-sectional views of FIGS. 10A to 10C simultaneously for convenienceof description.

As shown in FIG. 9A, a unit cell L1E contains a first reflection section11A1 and a second reflection section 11A2. The inclination angle θformed by the reflection surface 11S of the first reflection section11A1 and the display surface 10S is equal to the inclination angle θformed by the reflection surface 11S of the second reflection section11A2 and the display surface 10S, but the second reflection section 11A2has a smaller height than first reflection section 11A1.

FIG. 10A shows the cross-sectional structure in an XZ plane that istaken along line I-I in FIG. 9A. In this cross section in the XZ plane,the first reflection section 11A1 has a first oblique side SL1, and thesecond reflection section 11A2 has a second oblique side SL2. The firstoblique side SL1 is longer than the second oblique side SL2 and may bedouble the length of the second oblique side SL2. The width of eachreflection section in the X direction, or the arrangement direction ofthe reflection sections, is a structure width, which is preferablywithin the range described above.

FIG. 9B shows a unit cell L1E that contains a first reflection section11A1, a second reflection section 11A2, and a third reflection section11A3. The inclination angle θ formed by the reflection surface 11S ofthe first reflection section 11A1 and the display surface 10S, theinclination angle θ formed by the reflection surface 11S of the secondreflection section 11A2 and the display surface 10S, and the inclinationangle θ formed by the reflection surface 11S of the third reflectionsection 11A3 and the display surface 10S are all identical. Of the threereflection sections, the first reflection section 11A1 is substantiallyequal to the second reflection section 11A2 in height. The height of thethird reflection section 11A3 is less than the heights of the firstreflection section 11A1 and the second reflection section 11A2. Thesecond reflection section 11A2 and the third reflection section 11A3 areeach shaped as a triangular prism. The first reflection section 11A1 hasa shape in which a triangular prism is connected to the upper side of arectangular prism as viewed in the figure. In other words, the firstreflection section 11A1 includes a first section that is shaped as arectangular prism and a second section that is shaped as a triangularprism. The second section is located on top of the first section.

FIG. 10B shows the cross-sectional structure in an XZ plane that istaken along line II-II in FIG. 9B. In this cross section in the XZplane, the first reflection section 11A1 has a first oblique side SL1,the second reflection section 11A2 has a second oblique side SL2, andthe third reflection section 11A3 has a third oblique side SL3. Of thethree reflection sections, the second reflection section 11A2 has thelongest oblique side, followed by the third reflection section 11A3 andthen the first reflection section 11A1. However, two of the threeoblique sides may be equal in length, or all the oblique sides may beequal in length.

The three reflection sections include reflection sections having theshape of a triangular prism and a reflection section having the shape ofa combination of a triangular prism and a rectangular prism. That is,the three reflection sections include reflection sections that havedifferent outer shapes. This limits diffraction of light, which wouldotherwise occur when three reflection sections are arranged in the Xdirection, as compared with a configuration in which the threereflection sections only include reflection sections of the identicalouter shapes.

FIG. 9C shows a structure in which the reflection sections of FIG. 9Bare rotated by 45° about the axis in the Z direction in the clockwisedirection as viewed in the figure. That is, the azimuth angle Φ ofreflection sections of FIG. 9B differs from the azimuth angle Φ of thereflection sections of FIG. 9C.

FIG. 10C shows the cross-sectional structure taken along line III-III inFIG. 9C. That is, FIG. 10C shows the cross-sectional structure along aplane extending in the Z direction and the direction that intersectswith the X direction at an angle of 45°. This plane includes a diagonalline of the unit cell L1E. The cross-sectional structure along lineIII-III shown in FIG. 10C is identical to the cross-sectional structurealong line II-II shown in FIG. 10B.

In geometrical optics, the light reflected by the reflection surface 11Sdoes not spread. However, the diffraction phenomenon occurs when allreflection surfaces 11S have oblique sides of the same length in a crosssection including a plurality of reflection surfaces 11S, such as thecross sections shown in FIGS. 10A to 10C. The length of the obliquesides corresponds to the size of slit in the diffraction phenomenon. Thedisplay body according to the present disclosure uses visible light, andthe observation distance, which is the distance between the display bodyand the observer, is sufficiently long relative to the size of slit. Assuch, the Fraunhofer diffraction theory holds for the pixels of thedisplay body. Assuming that incident light on the reflection surface 11Shas a certain wavelength λ, the intensity I of the diffracted lightsatisfies Equation (A) below according to the slit size D, the wavenumber k, and the spreading angle ψ. I(0) represents the intensity ofregularly reflected light.

$\begin{matrix}{{I(\theta)} = {{I(0)}\left( \frac{\sin\;\beta}{\beta} \right)^{2}}} & {{Equation}\mspace{14mu}(A)} \\{\beta = {\left( \frac{k\; D}{2} \right)\sin\;\theta}} & {{Equation}\mspace{14mu}(B)}\end{matrix}$

FIG. 11A shows the intensity distribution of light diffracted when theslit size D is 10 μm, FIG. 11B shows the intensity distribution of lightdiffracted when the slit size D is 20 μm, and FIG. 11C shows theintensity distribution of light diffracted when the slit size D is 50μm. The intensity distributions shown in FIGS. 11A to 11C are obtainedassuming that the wavelength λ of incident light is 555 nm, which hasthe highest relative luminosity in the wavelength range of visiblelight. For the sake of simplicity, it is assumed that the oblique sidesof the reflection surfaces 11S are not inclined.

As is evident from FIGS. 11A to 11C, different slit sizes D, or lengthsof the oblique sides of the reflection surfaces 11S, result in differentstates of diffraction of light reflected at the reflection surfaces 11Sand thus different intensity distributions of diffracted light. In allof the intensity distributions of diffracted light, the intensity oflight emerged in the direction of regular reflection of the reflectionsurface 11S is the highest regardless of the slit size D. The angularrange of light emerged in the direction of regular reflection is aspreading angle. The spreading angle of the light emerged in thedirection of regular reflection is the largest when the slit size D is10 μm and the smallest when the slid size D is 50 μm. That is, a largerslit size D reduces the spreading angle of the light emerged in thedirection of regular reflection.

The angular range of light that can be incident on the pupils of theobserver of the display body is ±0.5°. When the amount of light incidenton a reflection surface 11S is 100%, the amount of light reflected bythe reflection surface 11S, or the pixel, is 32% when the slit size D is10 μm, 58% when the slit size is 20 μm, and 90% when the slit size D is50 μm. A greater slit size D, or a longer oblique side, increases theamount of light perceived by the observer and thus increases thebrightness of the display body.

The display body may have multiple types of pixels having different slitsizes D, or pixel sizes. Different pixel sizes result in differentintensity distributions of diffracted light. As such, the display bodyof this configuration includes pixels with which the observer perceivesdifferent amounts of light. The pixel size may vary from pixel group topixel group, which is formed of a plurality of pixels.

FIG. 12 shows the cross-sectional structure of a display body 10. Asshown in FIG. 12, the display body 10 may include a substrate 12 and aplurality of pixels 11A described above. In this structure, the surface12S of the substrate 12 on which the pixels 11A are located correspondsto the display surface 10S described above. The observation side of thedisplay body 10 may be the first observation side that is opposite tothe substrate 12 with respect to the pixels 11A, or the secondobservation side that is opposite to the pixels 11A with respect to thesubstrate 12. When the observation side of the display body 10 is thesecond observation side, the substrate 12 needs to be lighttransmissive.

FIG. 13 schematically shows the light incident on the display body 10and the light emerged ted from the display body 10 when the observationside of the display body 10 is the second observation side. In thisexample, an observer OB views the display body 10 such that a planeincluding the observation direction DO of the observer OB isperpendicular to the XY plane extending along the display surface 10S.Further, in the example of FIG. 13, the display body 10 is set such thatthe substrate 12 extends in the Y direction.

As shown in FIG. 13, when observing the display body 10, the observer OBtends to tilt the display body 10 such that the inclination angle Θformed by the surface 12S of the substrate 12 and the horizontal planeHR is about 45°. In addition, light is typically incident on the displaybody 10 from directly above the observer OB, such as the case ofsunlight and light from a fluorescent lamp located on the ceiling.

In this case, in order for the incident light Lin on the reflectionsurface 11S of the display body 10 to be reflected by the reflectionsurface 11S and emerged as outgoing light Lout toward the observationside, the azimuth angle Φ of the reflection surface 11S preferablycorresponds to the direction symmetrical to the observation direction DOof the observer OB. That is, the azimuth angle Φ is preferably 0°. Whenthe azimuth angle Φ is 0°, the observer OB perceives the reflected lightwith the highest intensity. The larger the difference between 0° and theazimuth angle Φ of the reflection surface 11S, the lower the intensityof light perceived by the observer OB, so that the observer OB feelsthat the lightness of the display body 10 is low.

The azimuth angle Φ of the reflection surfaces 11S when the display body10 is observed from the first observation side and the azimuth angle Φof the reflection surfaces 11S when the display body 10 is observed fromthe second observation side are symmetric with respect to the linepassing through positions corresponding to azimuth angles Φ of 90° and270°.

That is, as shown in FIG. 14A, when the display body 10 is observed fromthe first observation side, the direction of the normal to thereflection surface 11S is a first direction D1. As shown in FIG. 14B,when the display body 10 is observed from the second observation side,the direction of the normal to the reflection surface 11S is a seconddirection D2, which is laterally symmetrical to the first direction D1as viewed in the figure. Thus, when the azimuth angle Φ of the displaybody 10 observed from the second observation side is 0°, the azimuthangle Φ of the display body 10 observed from the first observation sideis 180°.

The observer OB not only observes the display body 10 while holding itinclined at a fixed angle from the horizontal plane HR but also observesthe display body 10 while varying the inclination of the display body 10from the horizontal plane HR. As described above, when the inclinationangle Θ between the display surface 10S and the horizontal plane HR isabout 45°, an azimuth angle Φ of 0° provides the light that is perceivedby the observer OB with the highest intensity.

When the display body 10 is tilted in the front-back direction, of thelight reflected by the reflection surface 11S with an azimuth angle Φ of0°, the light perceived by the observer OB decreases in intensity. Inother words, when the display surface 10S is tilted such that thesection of the display surface 10S that intersects with a planeincluding the observation direction of the observer OB and extendingalong the X direction and the section of the plane including theobservation direction that intersects with the display surface 10Sremain unchanged, of the light reflected from the reflection surface 11Shaving an azimuth angle Φ of 0°, the light perceived by the observer OBdecreases in intensity. In contrast, of the light reflected by thereflection surface 11S with an azimuth angle Φ of 180°, the light thatis perceived by the observer OB increases in intensity.

As such, the image of the display body 10 appears and disappearsdepending on the combination of the azimuth angle Φ of the reflectionsurfaces 11S and the inclination angle Θ between the display surface 10Sand the horizontal plane HR.

Referring to FIGS. 15 to 16B, an example is described in which theobserver OB perceives an image that changes when the angle formed by thedisplay surface 10AS of the display body 10A and the plane including theobservation direction of the observer OB changes. As described above,when the Y direction in FIGS. 15 to 16B coincides with the projectiondirection of the reflection surface of a pixel 11A, the azimuth angle Φof the reflection surface is 0°.

As shown in FIG. 15, the display body 10A has a display surface 10AS,which includes a first region group AS1 for displaying a first image P1and a second region group AS2 for displaying a second image P2. Thefirst and second region groups AS1 and AS2 each include a plurality ofpixels 11A. In this example, in a plan view of the display surface 10AS,the first region group AS1 has a crescent shape, and the second regiongroup AS2 has a star shape.

The section of the display surface 10AS other than the first and secondregion groups AS1 and AS2 may include pixels 11A or may be free ofpixels 11A. However, when the section of the display surface 10AS otherthan the first and second region groups AS1 and AS2 includes pixels 11Aand all the pixels 11A have the same azimuth angle Φ, the pixels 11A ofa certain shape are arranged on the display surface 10AS with a fixedperiodicity. This increases the likelihood that diffracted light isemerged from the display surface 10AS. The diffracted light may lowerthe visibility of the first and second images P1 and P2.

In contrast, when the section of the display body 10A other than thefirst and second region groups AS1 and AS2 is free of pixels 11A,tilting of the display body 10A causes only a small change in intensityof the light reflected from the region group that is free of pixels 11A.This maintains a constant contrast between the section that is free ofpixels 11A and the first and the second images P1 and P2, therebyincreasing the visibility of the images.

The range of azimuth angles Φ of the pixels 11A in the first regiongroup AS1 is a first range, and the range of azimuth angles Φ of thepixels 11A in the second region group AS2 is a second range. The firstrange differs from the second range. The minimum value of the differencebetween the azimuth angles Φ included in the first range and the azimuthangles Φ included in the second range is preferably greater than orequal to 30°.

For example, when the azimuth angles Φ in the first range are greaterthan the azimuth angles Φ in the second range, the first range isgreater than or equal to 90° and less than 180° and the second range isbetween 0° and 60° inclusive. In this case, the minimum value of thedifference between the azimuth angles Φ in the first range and theazimuth angles Φ in the second range is 30°. When the difference betweenthe azimuth angles Φ in the first range and the azimuth angles Φ in thesecond range is greater than or equal to 30°, the first and secondimages P1 and P2 are less likely to be perceived as forming a singleimage.

The azimuth angles Φ in the first and second ranges may be greater thanor equal to 0° and less than 180°, or greater than or equal to 180° andless than 360°. For example, the first range may be greater than orequal to 120° and less than 180°, and the second range may be between15° and 60° inclusive. The difference between the minimum azimuth angleΦ in the second range and the maximum azimuth angle Φ in the first rangeis preferably less than 180°.

This configuration advantageously reduces the possibility that the lightemerged by the first region group AS1 and the light emerged by thesecond region group AS2 are perceived by the observer OB as forming asingle image when the observer OB tilts the display body 10A such thatthe section of the display body 10A that intersects with the planeincluding the observation direction and extending along the X directionand the section of the plane including the observation direction thatintersects with the display body 10A remain unchanged but the angleformed by the display body 10A and the plane including the observationdirection is changed.

As described for the first embodiment, the plurality of pixels 11Abelonging to each of the first region group AS1 and the second regiongroup AS2 includes pixels 11A that include reflection surfaces 11S ofdifferent orientations, or azimuth angles Φ. However, the azimuth anglesΦ of all reflection surfaces 11S may be identical in each region group.

Referring to FIGS. 16A and 16B, the operation of an example of a displaybody 10A is described in which the azimuth angles Φ in the first rangeare greater than or equal to 120° and less than 180° and the azimuthangles Φ in the second range are between 15° and 60° inclusive. Thefollowing operation is achieved also with a display body 10A in whichthe azimuth angles Φ in the first range and the azimuth angles Φ in thesecond range are greater than or equal to 180° and less than 360°.

As shown in FIG. 16A, the observer OB holds the display body 10A suchthat the display surface 10AS of the display body 10A is perpendicularto the plane including the observation direction DO of the observer OB.In addition, the observer OB holds the display body 10A such that thefirst region group AS1 is positioned above the second region group AS2in the Y direction in the display surface 10AS, that is, the secondregion group AS2 is closer to the hand of the observer OB than the firstregion group AS1.

In this position, the observer OB perceives the first image P1 displayedby the first region group AS1 but cannot perceive the second image P2displayed by the second region group AS2.

Then, as shown in FIG. 16B, the observer OB tilts the display body 10Ain the front-back direction, that is, in the projection directioncorresponding to an azimuth angle Φ of 0° and the projection directioncorresponding to an azimuth angle Φ of 180°. In other words, theobserver OB tilts the display body 10A so as to reduce one of the anglesformed by the display surface 10AS and the plane including theobservation direction DO and extending along the X direction, withoutchanging the observation direction DO of the observer OB.

Specifically, the observer OB tilts the display body 10A so as toreduce, of the two angles formed on opposite sides of the planeincluding the observation direction DO, the angle closer to the observerOB, or the angle on the lower side of the plane including theobservation direction DO in the Y direction. In other words, theobserver OB tilts the display body 10A such that both of the section ofthe display surface 10AS of the display body 10A that intersects withthe plane including the observation direction DO and the section of theplane including the observation direction DO that intersects with thedisplay surface 10AS remain unchanged.

In this position, the observer OB perceives the second image P2displayed by the second region group AS2 but cannot perceive the firstimage P1 displayed by the first region group AS1.

The display body 10A displays an image that is switched between thefirst image P1 and the second image P2 depending on the angle formed bythe display surface 10AS of the display body 10A and the plane includingthe observation direction DO of the observer OB.

The azimuth angles Φ in the first range and the azimuth angles Φ in thesecond range may be greater than or equal to 90° and less than 180°, orgreater than or equal to 180° and less than 270°. In this case, theimage displayed by the display body 10A is switched between the firstimage P1 and the second image P2 when the observer OB tilts the displaybody 10A as follows.

That is, when the display body 10A is tilted in the lateral direction,or the projection direction corresponding to an azimuth angle Φ of 90°and the projection direction corresponding to an azimuth angle Φ of270°, the image displayed by the display body 10A is switched betweenthe first image P1 and the second image P2.

In other words, when observing the display body 10A, the observer OBtilts the display body 10A, from the position in which the displaysurface 10AS of the display body 10A is perpendicular to the planeincluding the observation direction DO of the observer OB and extendingalong the X direction, such that the section of the display surface 10ASof the display body 10A that intersects with the plane including theobservation direction DO remains unchanged but the section of the planeincluding the observation direction DO that intersects with the displaybody 10A is changed.

As compared with the configuration described above, this configurationtends to cause multiple reflection of the light incident on the displaysurface 10AS when the inclination angle θ of the reflection surface 11Sof each pixel 11A is relatively large. The multiple reflection may causeoverlapping between the first and second images P1 and P2. As such, thereflection surface 11S of each pixel 11A preferably has an inclinationangle θ that does not cause multiple reflection of the light incident onthe display surface 10AS.

FIG. 17 shows a display body 10B that has a display surface 10BS andincludes a first region group BS1, a second region group BS2, and athird region group BS3. The display body 10B displays a first image P1and a second image P2. The first image P1 is displayed by the first andthird region groups BS1 and BS3. The second image P2 is displayed by thesecond and third region groups BS2 and BS3. In this example, the firstimage P1 has a crescent shape, and the second image P2 has a star shape.

The first region group BS1 includes a plurality of unit cells LiE, eachof which may contain one first pixel for displaying the first image P1.The second region group BS2 includes a plurality of unit cells LiE, eachof which may contain one second pixel for displaying the second imageP2. The third region group BS3 includes a plurality of unit cells LiE,some of which contain first pixels and the others contain second pixels.The section of the display surface 10BS other than the first to thirdregion groups BS1 to BS3 may include pixels or may be free of pixels.

The first range of the azimuth angles Φ of the first pixels and thesecond range of the azimuth angles Φ of the second pixels preferablyhave a similar relationship as the first range and the second range ofthe display body 10A described above. Further, the section of thedisplay surface 10BS other than the first to third region group BS1 toBS3 is preferably free of pixels because of the reason described abovefor the display body 10A.

In the third region group BS3, the plurality of first pixels and theplurality of second pixels may be arranged in a checkered pattern or ina stripe pattern. The third region group BS3 includes equal numbers offirst pixels and second pixels. Each of the unit cells L1E in the thirdregion group BS3 contains one of a first pixel and a second pixel.

All of the unit cells L1E in the first region group BS1 can containfirst pixels, and all of the unit cells L1E in the second region groupBS2 can contain second pixels. In this case, however, the section of thefirst image P1 displayed by the first region group BS1 differs inlightness from the section of the first image P1 displayed by the thirdregion group BS3, and the section of the second image P2 displayed bythe second region group BS2 differs in lightness from the section of thesecond image P2 displayed by the third region group BS3.

In this respect, the proportion of the unit cells L1E having firstpixels in the first region group BS1 is preferably equal to that in thethird region group BS3, and the proportion of the unit cells L1E havingsecond pixels in the second region group BS2 is preferably equal to thatin the third region group BS3.

On a display surface that displays multiple images, when one regiongroup includes equal numbers of different types of pixels, eachdisplaying a corresponding one of the different images, the proportionof one type of pixels displaying an image in the unit cells ispreferably the reciprocal of the number of images in each of the regiongroups including pixels.

A display body may display four images, and one region group in thedisplay surface of the display body may include four types of pixelsthat display their respective images. The four types of pixels may bearranged in one of the first, second, and third arrangements.

The first arrangement sets four types of pixels in stripes, and fourlines of mutually different types of pixels form one periodicity. Thesecond arrangement sets the pixels of different types in lines forming45° with the X direction. In the same manner as the first arrangement,the four lines of mutually different types of pixels form oneperiodicity in the second arrangement. The third arrangement sets pixelsof four different types about one grid point of unit cells L1E so thatthe four types of pixels are arranged next to one another.

When one side of a unit cell L1E corresponds to 1, the periodicity ofpixels in the first arrangement corresponds to 4, the periodicity ofpixels in the second arrangement corresponds to 2√2, and the periodicityof pixels in the third arrangement corresponds to 2. The periodicitycorresponds to the resolution of the image. A smaller periodicity ofpixels is desirable to reduce the resolution of the image.

When the display body 10 is observed from the second observation side,the inclination angles θ of reflection surfaces 11S are preferably setas follows. An example of a display body 10 is described below in whichthe refractive index of the plurality of pixels 11A is equal to therefractive index of the substrate 12.

As shown in FIG. 18, when light is incident from directly above theobserver OB toward the display body 10, the incident light Lin isrefracted at the interface between air and the substrate 12, and isreflected at the reflection surface 11S of the pixel 11A. Then, thelight reflected at the reflection surface 11S is refracted at theinterface between the substrate 12 and air and is perceived as outgoinglight Lout by the observer OB.

Here, it is assumed that the inclination angle Θ between the displaysurface 10S, or the surface 12S of the substrate 12, and the horizontalplane HR is 45°, and the plane including the observation direction DO ofthe observer OB forms a right angle with the display surface 10S. Underthese conditions, the observer OB perceives light with the highestintensity when the angle γ formed by the outgoing light Lout and theincident light Lin is 45°.

To calculate the inclination angle θ of the reflection surface 11S,following Equation (5), which is Snell's law, is used.n1 sin α=n2 sin β  (5)

In Equation (5), n1 and n2 are the refractive indices of the mediums, αis the refraction angle of the incident light Lin, and β is therefraction angle of the outgoing light Lout. The refraction at theinterface between the display body 10 and air is described belowassuming that the refractive index of pixels 11A and the refractiveindex n1 of the substrate 12 are 1.5. The refractive index n2 of air is1.

As described above, the refraction at the interface between the displaybody 10 and air occurs on two occasions: the first occasion where theincident light Lin enters the display body 10 from air; and the secondoccasion where the light reflected by the reflection surface 11S isemerged from the display body 10 into air as the outgoing light Lout.

When the refraction angle of the incident light Lin is a refractionangle α and the refraction angle of the outgoing light Lout is arefraction angle β, Equation (6) holds for the first occasion, andEquation (7) holds for the second occasion.1 sin Θ=1.5 sin α  (6)1.5 sin(α−2θ)=sin β  (7)

Since the inclination angle Θ is 45°, the refraction angle α is 28.13°according to Equation (6). Further, Equation (8) holds when therefraction angle β is 0°.γ=Θ+β=45  (8)

Equation (9) is derived by substituting the refraction angle α, therefraction angle β, and Equation (8) into Equation (7).1.5 sin(28.13−2θ)=0  (9)

The inclination angle θ of the reflection surface 11S obtained fromEquation (9) is 14°.

The length in the X direction and the length in the Y direction of aunit cell L1E, in other words, the unit length, are preferably between 1μm and 300 μm inclusive. When the unit length is 1 μm or more, aplurality of pixels 11A arranged on the display surface 10S is lesslikely to produce diffracted light, limiting the possibility that thevisibility of the image P is lowered by diffracted light emerged fromthe display body 10. When the unit length is 300 μm or less, the pixels11A are unlikely to be visually recognized, and the resolution of thedisplay body 10 is not low.

Second Embodiment

A display body according to a second embodiment will now be describedwith reference to FIGS. 19 and 20. The image displayed by the displaybody is not limited to a raster image composed of repeated pixels, whichare examples of display regions, and may be a vector image composed of acollection of display regions represented by vectors. For convenience ofexplanation, the following description on a display body uses a pixel asan example of a display region and uses a collection of pixels fordisplaying an image in a single reflection direction as an example of adisplay pixel group. The configuration of the reflection surface forminga pixel is the same as that of the first embodiment. That is, thetraveling direction of the light reflected by the reflection surface maybe the direction in which light is diffracted by the reflection surfaceor may be a direction different from the direction in which light isdiffracted by the reflection surface. In the following example, thetraveling direction of reflected light coincides with the travelingdirection of diffracted light. The accompanying drawings are notnecessarily to scale and may include enlarged views of characteristicparts of the display body in order to clearly show its features.

FIG. 19 shows a display body 20 having a display surface 20S on whichpixels 21A are arranged in five lateral lines and five vertical lines.That is, in a plan view of the display surface 20S, pixels 21A arearranged in a matrix. The optical effect of the pixels 21A displays onthe display surface 20S a dynamic image that changes continuously inaccordance with changes in the direction in which the display body 20 isobserved. The image has a polygonal pattern formed by a matrix ofrectangular shapes.

The display surface 20S has a plurality of pixel groups 21Sa, 21Sb,21Sc, 21Sd and 21Se, each associated with a corresponding one of thetones in the image to be displayed. The pixels 21A forming the pixelgroups 21Sa to 21Se are located in their respective unit cells L2E,which are cells in a matrix of five vertical lines and five laterallines. That is, each unit cell L2E includes one pixel 21A.

In the present embodiment, of the pixels 21A shown in FIG. 19, all thepixels 21A arranged in the lateral direction in the first row form afirst pixel group 21Sa. Of the pixels 21A, all the pixels 21A arrangedin the lateral direction in the second row form a second pixel group21Sb. Of the pixels 21A, all the pixels 21A arranged in the lateraldirection in the third row form a third pixel group 21Sc. Of the pixels21A, all the pixels 21A arranged in the lateral direction in the fourthrow form a fourth pixel group 21Sd. Of the pixels 21A, all the pixels21A arranged in the lateral direction in the fifth row form a fifthpixel group 21Se.

The first to fifth pixel groups 21Sa to 21Se continuously vary inorientation of reflection surfaces in this order, and the correspondingdiffraction angles β may also continuously vary in this order. Each ofthe first to fifth pixel groups 21Sa to 21Se displays an image that isperceived with high brightness when the diffraction angle βcorresponding to the pixel group coincides with the reflection directionof the display body 20. On the other hand, when the correspondingdiffraction angle β does not coincide with the reflection direction ofthe display body 20, the image displayed by the pixel group 21Sa to 21Seis not easily perceived. That is, each of the first to fifth pixelgroups 21Sa to 21Se of the present embodiment displays a binary image ofwhite or black color depending on the reflection direction of thedisplay body 20, so that the image is perceived or not perceived by theobserver.

A white image is perceived when the intensity of the reflected lightemerged from pixels 21A is relatively high. A black image is perceivedwhen the intensity of the reflected light emerged from the pixels 21A isrelatively low and the reflected light is hardly perceived by theobserver.

As shown in the leftmost example in FIG. 20, none of the imagesdisplayed by the first to fifth pixel groups 21Sa to 21Se is perceivedwhen the display body 20 is observed from the front. All pixel groups21Sa to 21Se are perceived in black, in other words, in the backgroundcolor. When the direction in which the display body 20 is observed isshifted gradually from this state, the reflection direction of thedisplay body 20 first coincides with the direction corresponding to thediffraction angle β of the first pixel group 21Sa, allowing the imagedisplayed by the first pixel group 21Sa to be perceived with highbrightness. As the direction in which the display body 20 is observed isfurther shifted, the reflection direction of the display body 20coincides successively with the directions corresponding to thediffraction angles β of the second to fifth pixel groups 21Sb to 21Se,allowing the images displayed by the second to fifth pixel groups 21Sbto 21Se to be perceived successively with high brightness.

That is, in this example, when the direction in which the display body20 is observed is shifted gradually, laterally-extending element imagesare perceived successively as a dynamic image that moves from the upperside to the lower side of the display surface 20S as viewed in thefigure.

The effect that allows perception of the dynamic image that moves fromthe upper side to the lower side as viewed in the figure is achieved bythe structure in which the inclination angles θ of reflection surfaces11S vary sequentially in the order of the rows. This visual effect isalso achievable with a structure in which the light reflected by areflection surface 11S travels in a direction that differs from thedirection in which light is diffracted by the reflection surface 11S.

As described above, the second embodiment has the following advantage.

(9) In the image that is displayed when the direction in which thedisplay body 20 is observed is changed, the types of the element imagesare identical, and the positions of the element images differ from oneanother according to the reflection directions. Thus, when the directionin which the display body 20 is observed is changed, images of relatedbut different contents are displayed.

The second embodiment may also be formed as follows.

The following modifications may be used as a structure with which animage of a polygonal pattern is displayed dynamically when the directionin which the display body 20 is observed is continuously shifted.

FIG. 21A shows the first example of a display body. Of the pixels 21Aarranged in a matrix, the pixels 21A on the diagonal line connecting theupper left corner to the lower right corner as viewed in the figuremoves toward the upper right and toward the lower left in the dynamicimage as the reflection direction of each display region group changes.

FIG. 21B shows the second example. In this display body, when thereflection direction of each display region group changes, the binaryimages of the pixels 21A arranged in a matrix are switched such thatblack images and white images are evenly distributed over the displaysurface 20S.

That is, each of the pixels 21A arranged in a matrix displays a binaryimage of white or black color depending on the reflection direction ofthe display region group, so that the image is perceived or notperceived by the observer.

FIG. 21C shows the third example. In this display body, as thereflection direction of each display region group changes, eachlaterally-extending image moves from the upper side to the lower side ofthe display surface 20S as viewed in the figure. In addition, thetrajectory of the movement of the image is expressed by the gradation oflight and shade of images, that is, the variation in intensity of thereflected light beams.

This may be achieved by reducing the differences between the diffractionangles β of the first to fifth pixel groups 21Sa to 21Se. With thisstructure, as shown in the leftmost example in FIG. 21C, none of theimages displayed by the first to fifth pixel groups 21Sa to 21Se isperceived when the display body 20 is observed from the front. All pixelgroups 21Sa to 21Se are perceived in black, in other words, in thebackground color. When the direction in which the display body 20 isobserved is shifted gradually from this state, the reflection directionof the display body 20 coincides with the direction corresponding to thediffraction angle β of the first pixel group 21Sa, allowing the imagedisplayed by the first pixel group 21Sa to be perceived with highbrightness.

When the direction in which the display body 20 is observed is furthershifted from this state, the direction in which the display body 20 isobserved coincides with the direction corresponding to the diffractionangle β of the second pixel group 21Sb, allowing the image displayed bythe second pixel group 21Sb to be perceived with high brightness. Atthis time, since the difference between the direction in which thedisplay body 20 is observed and the direction corresponding to thediffraction angle β of the first pixel group 21Sa is small, the imagedisplayed by the first pixel group 21Sa is also perceived with aslightly reduced brightness. That is, the image displayed by the firstpixel group 21Sa is perceived as an image that has a lower brightnessthan the image displayed by the second pixel group 21Sb and has a higherbrightness than the images displayed by the third to fifth pixel groups21Sc to 21Se.

When the direction in which the display body 20 is observed is furthershifted from this state, the reflection direction of the display body 20coincides with the direction corresponding to the diffraction angle β ofthe third pixel group 21Sc, allowing the image displayed by the thirdpixel group 21Sc to be perceived with high brightness. Again, since thedifference between the direction in which the display body 20 isobserved and the direction corresponding to the diffraction angle β ofthe second pixel group 21Sb is small, the image displayed by the secondpixel group 21Sb is also perceived with a slightly reduced brightness.Further, since the difference between the direction in which the displaybody 20 is observed and the direction corresponding to the diffractionangle β of the first pixel group 21Sa is still relatively small, theimage displayed by the first pixel group 21Sa is also perceived with afurther reduced brightness. That is, the images displayed by the firstto third pixel groups 21Sa, to 21Sc are perceived, with the image of thethird pixel group 21Sc having the highest brightness, followed by theimage of the second pixel group 21Sb and then the image of the firstpixel group 21Sa.

That is, with this configuration, when the direction in which thedisplay body 20 is observed coincides with the direction correspondingto the diffraction angle β of one of the first to fifth pixel groups21Sa to 21Se, the differences between the observation direction and thedirections corresponding to the diffraction angles β of the other pixelgroups 21Sa to 21Se are relatively small. Consequently, as the directionin which the display body 20 is observed is further shifted, after theimage of one of the first to fifth pixel groups 21Sa to 21Se isdisplayed with high brightness, the image of this pixel group isperceived with a reduced brightness together with the image displayed byanother pixel group.

Third Embodiment

A display body according to a third embodiment will now be describedwith reference to FIGS. 22 and 23. The image displayed by the displaybody is not limited to a raster image composed of repeated pixels, whichare examples of display regions, and may be a vector image composed of acollection of display regions represented by vectors. For convenience ofexplanation, the following description on a display body uses a pixel asan example of a display region and uses a collection of pixels fordisplaying an image in a single reflection direction as an example of adisplay pixel group. The configuration of the reflection surface forminga pixel is the same as that of the first embodiment. That is, thetraveling direction of the light reflected by the reflection surface maybe the direction in which light is diffracted by the reflection surfaceor may be a direction different from the direction in which light isdiffracted by the reflection surface. In the following example, thetraveling direction of reflected light coincides with the travelingdirection of diffracted light. The accompanying drawings are notnecessarily to same scale or aspect ratio as actual and may includeenlarged views of characteristic parts of the display body in order toclearly show its features.

As shown in FIG. 22, a display body 30 includes a display surface 30S,in which a plurality of pixels 31A is arranged in a matrix. Each pixel31A is located in a unit cell L3E of a triangular lattice. The opticaleffect of the pixels 31A displays on the display surface 30S a dynamicimage that varyes continuously in accordance with shifts in thedirection in which the display body 30 is observed. The image has apolygonal pattern in which multiple pixels 31A are combined.

The display surface 30S has a plurality of pixel groups 31Sa to 31Se,each associated with a corresponding one of the tones in the image to bedisplayed. The pixels 31A forming the pixel groups 31Sa to 31Se arelocated in their respective unit cell L3E, which are cells in thematrix. That is, each unit cell L3E includes one pixel 31A.

In the present embodiment, of the pixels 31A shown in FIG. 22, all thepixels arranged in the lateral direction in the bottom row as viewed inthe figure form a first pixel group 31Sa. Of the pixels 31A, all thepixels arranged in the lateral direction in the second row from thebottom as viewed in the figure form a second pixel group 31Sb. Of thepixels 31A, all the pixels arranged in the lateral direction in thethird row from the bottom as viewed in the figure form a third pixelgroup 31Sc. Of the pixels 31A, the pixel arranged in the lateraldirection in the fourth row from the bottom as viewed in the figureforms a fourth pixel group 31Sd. Of the pixels 31A, the pixel in the toprow as viewed in the figure forms a fifth pixel group 31Se.

The first to fifth pixel groups 31Sa to 31Se continuously vary inorientation of reflection surfaces in this order, and the correspondingdiffraction angles β also vary continuously in this order. Each of thefirst to fifth pixel groups 31Sa to 31Se displays an image that isperceived with high brightness when the corresponding diffraction angleβ coincides with the reflection direction of the display region group.When the corresponding diffraction angle β does not coincide with thereflection direction of the display region group, the image displayed bythe pixel group 31Sa to 31Se is not easily perceived. That is, each ofthe first to fifth pixel groups 31Sa to 31Se of the present embodimentdisplays a binary image of white or black color depending on thedirection in which the display body 30 is observed, so that the image isperceived or not perceived by the observer.

As shown in the leftmost example in FIG. 23, none of the imagesdisplayed by the first to fifth pixel groups 31Sa to 31Se is perceivedwhen the display body 30 is viewed from the front. All pixel groups 31Sato 31Se are perceived in black, in other words, in the background color.When the direction in which the display body 30 is observed is shiftedgradually from this state, the direction in which the display body 30 isobserved coincides with the direction corresponding to the diffractionangle β of the first pixel group 31Sa, allowing the image displayed bythe first pixel group 31Sa to be perceived with high brightness. Then,as the direction in which the display body 30 is observed is furthershifted, the observation direction successively coincides with thedirections corresponding to the diffraction angles β of the second tofifth pixel groups 31Sb to 31Se, allowing the images displayed by thesecond to fifth pixel groups 31Sb to 31Se to be perceived with highbrightness.

That is, in this example, as the direction in which the display body 30is observed is shifted gradually, laterally-extending element images areperceived successively as a dynamic image that moves from the bottom rowto the top row in the display surface 30S as viewed in the figure.

The effect that allows perception of the dynamic image that moves fromthe upper side to the lower side as viewed in the figure is achieved bythe structure in which the inclination angles θ of reflection surfaces11S vary sequentially in the order of the rows. This visual effect isalso achievable with a configuration in which the light reflected by thereflection surface 11S travels in a direction that differs from thedirection in which light is diffracted by the reflection surface 11S.

As described above, the third embodiment has the same advantage as thesecond embodiment.

The third embodiment may also be formed as follows.

The following modifications may be used as a structure with which animage of a polygonal pattern is displayed dynamically when the directionin which the display body 30 is observed is continuously shifted.

FIG. 24A shows the first example. In this display body,laterally-extending images move from the bottom row to the top row ofthe display surface 30S as viewed in the figure as the direction inwhich the display body is observed is shifted. In addition, thetrajectory of the movement of each image is expressed with the gradationof light and shade, that is, the intensities of the reflected lightbeams.

This may be achieved by reducing the differences between the diffractionangles β corresponding to the first to fifth pixel groups 31Sa to 31Se.As shown in the leftmost example in FIG. 24A, none of the imagesdisplayed by the first to fifth pixel groups 31Sa to 31Se is perceivedwhen the display body 30 is observed from the front. All pixel groups31Sa to 31Se are perceived in black, in other words, in the backgroundcolor.

When the direction in which the display body 30 is observed is shiftedgradually from this state, the direction in which the display body 30 isobserved first coincides with the direction corresponding to thediffraction angle β of the first pixel group 31Sa, allowing the imagedisplayed by the first pixel group 31Sa to be perceived with highbrightness.

When the direction in which the display body 30 is observed is furthershifted from this state, the direction in which the display body 30 isobserved coincides with the direction corresponding to the diffractionangle β of the second pixel group 31Sb, allowing the image displayed bythe second pixel group 31Sb to be perceived with high brightness. Atthis time, since the difference between the direction in which thedisplay body 30 is observed and the direction corresponding to thediffraction angle β of the first pixel group 31Sa is small, the imagedisplayed by the first pixel group 31Sa is also perceived with aslightly reduced brightness. That is, the image displayed by the firstpixel group 31Sa is perceived as an image that has a lower brightnessthan the image displayed by the second pixel group 31Sb and has a higherbrightness than the images displayed by the third to fifth pixel groups31Sc to 31Se.

When the direction in which the display body 30 is observed is furthershifted from this state, the direction in which the display body 30 isobserved coincides with the direction corresponding to the diffractionangle β of the third pixel group 31Sc, allowing the image displayed bythe third pixel group 31Sc to be perceived with high brightness. Again,since the difference between the direction in which the display body 30is observed and the direction corresponding to the diffraction angle βof the second pixel group 31Sb is small, the image displayed by thesecond pixel group 31Sb is also perceived with a slightly reducedbrightness. Further, since the difference between the direction in whichthe display body 30 is observed and the direction corresponding to thediffraction angle β of the first pixel group 31Sa is still relativelysmall, the image displayed by the first pixel group 31Sa is alsoperceived with a further reduced brightness.

That is, with this configuration, when the reflection direction of eachdisplay region group coincides with the direction corresponding to thediffraction angle β of one of the first to fifth pixel groups 31Sa to31Se, the differences between the reflection direction and thedirections corresponding to the diffraction angles β of the other pixelgroups are relatively small. Consequently, as the direction in which thedisplay body is observed is gradually shifted, after the image of one ofthe first to fifth pixel groups 31Sa to 31Se is displayed with highbrightness, the image of this pixel group is perceived with a reducedbrightness together with the image displayed by another pixel group.

FIG. 24B shows the second example. In this display body, a collection ofpixels 31A is arranged in a pyramid shape. Parts of the collection eachfunction as one of three regions R1, R2 and R3. In each of the regionsR1, R2 and R3, the orientations of the reflection surfaces of the pixels31A vary in steps of constant rate with respect to the pixel in the toprow as viewed in the figure. As such, when viewed from a givenreflection direction, the collection of the pixels 31A in each regiondisplays an image with a gradation of light and shade, in other words,an image with various intensities of reflected light beams. The regionslocated on the left and right sides in the lower row are regions R1. Thepixel 31A in the top row in each region R1 forms a first pixel group31Sa.

The region in the middle in the lower row is the region R2. The pixel31A in the bottom row in the region R2 forms a second pixel group 31Sb.The region in the upper row is the region R3, and the pixel 31A in thetop row in the region R3 forms a third pixel group 31Sc. The first tothird pixel groups 31Sa to 31Sc continuously vary in orientation ofreflection surfaces in this order, and the corresponding diffractionangles β also vary continuously in this order.

As shown in the leftmost example in FIG. 24C, when the display body 30is observed from the front, the direction in which the display body 30is observed coincides with the direction corresponding to thediffraction angle β of the first pixel group 31Sa. At this time, thecollection of the first pixel group 31Sa and the pixels 31A, thereflection surfaces of which vary in steps of uniform rate with respectto the first pixel group 31Sa in orientation, in each region R1 isperceived with high brightness.

When the direction in which the display body 30 is observed is shiftedgradually from this state, the direction in which the display body 30 isobserved coincides with the direction corresponding to the diffractionangle β of the second pixel group 31Sb. At this time, the collection ofthe second pixel group 31Sb and the pixels 31A, the reflection surfacesof which vary in steps of uniform rate with respect to the second pixelgroup 31Sb in orientation, in the region R2 is perceived with highbrightness. The difference between the direction in which the displaybody 30 is observed and the direction corresponding to the diffractionangle β of the first pixel group 31Sa is small. Thus, the imagedisplayed by the collection of the first pixel group 31Sa and the pixels31A, the reflection surfaces of which vary in steps of uniform rate withrespect to the first pixel group 31Sa in orientation, in each region R1is also perceived with a slightly reduced brightness.

When the direction in which the display body 30 is observed is furthershifted from this state, the direction in which the display body 30 isobserved coincides with the direction corresponding to the diffractionangle β of the third pixel group 31Sc. At this time, the image displayedby the collection of the third pixel group 31Sc and the pixels 31A, thereflection surfaces of which vary in steps of uniform rate with respectto the third pixel group 31Sc in orientation, in the region R3 isperceived with high brightness. Again, the difference between thedirection in which the display body 30 is observed and the directioncorresponding to the diffraction angle β of the second pixel group 31Sbis small. Thus, the image displayed by the collection of the secondpixel group 31Sb and the pixels 31A, the reflection surfaces of whichvary in steps of uniform rate with respect to the second pixel group31Sb in orientation, in the region R2 is also perceived with a slightlyreduced brightness.

In addition, the difference between the direction in which the displaybody 30 is observed and the direction corresponding to the diffractionangle β of the first pixel group 31Sa is still relatively small. Thus,the image displayed by the collection of the first pixel group 31Sa andthe pixels 31A, the reflection surfaces of which vary in steps ofuniform rate with respect to the first pixel group 31Sa in orientation,in each region R1 is also perceived with a further reduced brightness.

That is, with this configuration, when the direction in which thedisplay body 30 is observed coincides with the direction correspondingto the diffraction angle β of one of the first to third pixel groups31Sa to 31Sc, the differences between the observation direction and thedirections corresponding to the diffraction angles β of the other pixelgroups are relatively small. Consequently, as the direction in which thedisplay body 30 is observed is gradually shifted, after the image of oneof the first to third pixel groups 31Sa to 31Sc is displayed with highbrightness, this image is perceived with a reduced brightness togetherwith an image displayed by another pixel group.

Fourth Embodiment

A display body according to a fourth embodiment will now be describedwith reference to FIGS. 25A to 25C. The image displayed by the displaybody is not limited to a raster image composed of repeated pixels, whichare examples of display regions, and may be a vector image composed of acollection of display regions represented by vectors. For convenience ofexplanation, the following description on a display body uses a pixel asan example of a display region and uses a collection of pixels fordisplaying an image in a single reflection direction as an example of adisplay pixel group. The configuration of the reflection surface forminga pixel is the same as that of the first embodiment. That is, thetraveling direction of the light reflected by the reflection surface maybe the direction in which light is diffracted by the reflection surfaceor may be a direction different from the direction in which light isdiffracted by the reflection surface. In the following example, thetraveling direction of reflected light coincides with the travelingdirection of diffracted light. The accompanying drawings are notnecessarily to scale and may include enlarged views of characteristicparts of the display body in order to clearly show its features.

FIG. 25A shows a display body 40 that displays an image P representing ageometric three-dimensional structure as the element image. The displaybody 40 has pixels that differ from one another in orientation of thereflection surfaces, which are associated with regions of the image Pthat differ from one another in depth information. In the presentembodiment, the geometric three-dimensional structure is an apple. Inorder to represent the depth information of the three-dimensionalstructure by converting it into a gradation of light and shade, anappropriate tone value is set in advance for each region of thethree-dimensional structure. Each preset tone value is associated withan orientation of the reflection surface of a pixel. The tone values ofregions correspond to the tone values of the image used in themanufacturing of the display body 40.

The tone values of regions of the three-dimensional structure may beexpressed as follows. In the following description, a method forexpressing a 256 gradation, which is an example of a gradation, isdescribed.

As described above, when the inclination angle Θ between the displaysurface 40S of the display body 40 and the horizontal plane HR is about45° and the display body 40 is observed from the first observation side,the azimuth angle Φ of a reflection surface 11S interrelates with theintensity of light observed by the observer OB as follows. That is, whenthe azimuth angle Φ of a reflection surface 11S is 180°, the observer OBperceives the light with the highest intensity. The greater thedifference between the azimuth angle Φ of a reflection surface 11S and180°, the lower the intensity of light perceived by the observer OB.

Since the display body 40 is manufactured so as to provide 256 tones inthe image, when the azimuth angles Φ of all the reflection surfaces 11Sof the display body 40 are within the range of 90° and 180° inclusive,the azimuth angle Φ per tone is about 0.35°. The azimuth angle Φ pertone is calculated by dividing 90° by 255. Tone 0 corresponds to 90°,and tone 255 corresponds to 180°. Thus, a reflection surface 11S havingan azimuth angle Φ of 90.35° may be used for the region in the imagewhere the tone value is 1, and a reflection surface 11S having anazimuth angle Φ of 125° may be used for the region in the image wherethe tone value is 100.

The tones and the actual intensities, which are determined by theazimuth angles Φ, do not have to have a one-to-one correspondence. Forexample, when the maximum tone value is 100, a reflection surfaces 11Shaving an azimuth angle Φ of 180° may be used for the region in theimage where the tone value is 100. In this case, the azimuth angle Φ pertone can be calculated by dividing 90° by the value obtained bysubtracting the minimum tone value from the maximum tone value.

In the present embodiment, as shown in FIG. 25A, when the display body40 is viewed from the front, the entire image of the three-dimensionalstructure in the display surface 40S is perceived with low brightness.On the other hand, the entire region in the display surface 40S that isthe background of the three-dimensional structure is perceived with highbrightness.

Then, as the direction in which the display body 40 is observed isgradually shifted from this state, the directions corresponding to thediffraction angles β of the pixels associated with the regions in theimage P of the three-dimensional structure become close to the directionin which the display body 40 is observed, as compared with thedirections corresponding to the diffraction angles β of the pixelsassociated with the regions in the background of the three-dimensionalstructure. Accordingly, as shown in FIG. 25B, light and dark areinverted in the regions of the image P of the three-dimensionalstructure and the background region of the three-dimensional structuredisplayed by the display body 40.

As the direction in which the display body 40 is observed is furthershifted from this state, the direction in which the display body 40 isobserved becomes different from the directions corresponding to thediffraction angles β of the pixels associated with the shaded region inthe image P of the three-dimensional structure, reducing the brightnessof the shaded region in the image P of the three-dimensional structure.Accordingly, as shown in FIG. 25C, the contrast of light and darkbetween the regions of the three-dimensional structure displayed by thedisplay body 40 becomes clearer.

This visual effect that defines the direction of the movement of shadesin the image is achieved by the inclination angles θ of the reflectionsurfaces 11S of the pixels 11A that have a certain interrelation andvary sequentially with predetermined regularity. This visual effect ofdefining the direction of movement of shades in the image is alsoachievable by a structure in which the traveling direction of the lightreflected by the reflection surface 11S differs from the direction oflight diffracted by the reflection surface 11S.

As described above, the fourth embodiment has the following advantages.

(10) The image includes element images of the same type, and the elementimages have different shades depending on the direction in which thedisplay body 40 is observed. Thus, when the reflection direction ischanged, images of related but different contents are displayed.

(11) As the direction in which the display body 40 is observed isgradually varied, the contrast in the image also varies. The contrast inthe image is produced by the degrees of light and dark in the regions inthe image P of the three-dimensional structure. Accordingly, the image Pis displayed as a three-dimensional image, and the observer's perceptionof the image varies significantly as the reflection direction of thedisplay body 40 shifts.

The fourth embodiment may also be formed as follows.

The embodiment may be configured such that a region that has the highestlightness when the display body 40 is observed from a given reflectiondirection has the lowest lightness when the display body 40 is observedfrom a different reflection direction. Likewise, a region that has thelowest lightness when the display body 40 is observed from a givenreflection direction may have the highest lightness when the displaybody 40 is observed from a different reflection direction. Furthermore,the region that has the highest or lowest lightness when the displaybody 40 is observed in a given reflection direction may have thelightness of the intermediate value of the lightness values of thepixels in the display surface 40S when the display body 40 is observedfrom a different reflection direction.

FIG. 26 shows a display body 40A that displays an image P on the displaysurface 40AS. The image P may be of a polyhedron including a pluralityof surfaces Pf. In this modification, the image P includes twohexahedrons. One side of one of the hexahedrons is shared with theother.

The image P includes a plurality of display region groups ASg, eachformed by a plurality of pixels for displaying one surface Pf. Thereflection surfaces of the plurality of pixels belonging to each displayregion group ASg have an azimuth angle Φ that is common to the displayregion group ASg. In other words, each display region group ASg has anazimuth angle Φ unique to the display region group ASg. The azimuthangle Φ in each display region group ASg corresponds to the normaldirection NL to the surface Pf forming the polyhedron of the image P.

Specifically, as shown in FIG. 27, in a hemisphere protruding in the Zdirection from the XY plane including the display surface 40AS of thedisplay body 40A, the angle formed by the Z direction and the normaldirection NL to each surface Pf is referred to as a zenith angle θz. Aunique azimuth angle Φ is set for each surface Pf, or display regiongroup ASg, such that when a surface Pf have a larger zenith angle θz,the intensity of the light that is emerged by the surface Pf andperceived by the observer OB is lower. This allows the display body 40Ato display the image P of the polyhedron formed by a plurality ofsurfaces Pf. In the example described above, the observer OB observesthe display body 40A from such a direction that the plane including theobservation direction is perpendicular to the display surface 40AS, inother words, from the Z direction.

Fifth Embodiment

A display body according to a fifth embodiment will now be describedwith reference to FIGS. 28 and 29. The image displayed by the displaybody is not limited to a raster image composed of repeated pixels, whichare examples of display regions, and may be a vector image composed of acollection of display regions represented by vectors. For convenience ofexplanation, the following description on a display body uses a pixel asan example of a display region and uses a collection of pixels fordisplaying an image in a single reflection direction as an example of adisplay pixel group. The configuration of the reflection surface forminga pixel is the same as that of the first embodiment. That is, thetraveling direction of the light reflected by the reflection surface maybe the direction in which light is diffracted by the reflection surfaceor may be a direction different from the direction in which light isdiffracted by the reflection surface. In the following example, thetraveling direction of reflected light coincides with the travelingdirection of diffracted light. The accompanying drawings are notnecessarily to scale and may include enlarged views of characteristicparts of the display body in order to clearly show its features.

In FIG. 28, for the sake of convenience of illustrating the variation inheight of a pixel using a plane, the heights are expressed withgradations of lightness such that a position in a pixel that has agreater height in the Z direction has a lower lightness, in the samemanner as FIG. 8.

The display body of the fifth embodiment displays a three-dimensionalimage, which is an image of a three-dimensional structure, as with thedisplay body 40 of the fourth embodiment. Furthermore, this display bodydisplays different first and second images depending on the tiltingstate of the display body, as with the display body 10A of amodification of the first embodiment.

As shown in FIG. 28, a plurality of pixels 51A may include a pixel 51Athat is not large enough to occupy the largest area in the unit cell L1Eas viewed in the Z direction. Each unit cell L1E includes a pixel regionL1Ea, where a pixel 51A is located, and a surrounding region L1Eb, whichis the region outside the pixel region L1Ea. The pixel region L1Ea andthe unit cell L1E are similar or identical in shape. That is, the pixelregion L1Ea is square and smaller than the unit cell L1E.

The pixel region L1Ea and the unit cell L1E share the same center, allthe sides defining the pixel region L1Ea are located in the unit cellL1E so as to be parallel to at least one of the sides of the unit cellL1E. In each pixel region L1Ea, the pixel 51A is sized to occupy thelargest area in the pixel region L1Ea as viewed in the Z direction. Thatis, when a pixel 51A includes a plurality of reflection sections, thereflection sections are sized such that the area of reflection surfaces51S in the pixel 51A is maximized.

The surrounding region L1Eb is shaped as a square frame and located onthe outer side of the entire edge of the pixel region L1Ea. In otherwords, the surrounding region L1Eb surrounds the pixel region L1Ea.

As such, when the azimuth angles Φ of the reflection surfaces 51S areidentical, the area of the reflection surface 51S of the pixel 51Alocated in a pixel region L1Ea that is smaller than the unit cell L1E issmaller than the area of the reflection surface 51S of the pixel 51Athat is located in a pixel region L1Ea having the same size as the unitcell L1E. When the observer OB observes from a given observation point,a larger reflection surface 51S increases the intensity of the lightemerged from the pixel 51A and observed by the observer OB.

As such, the intensity of light per unit cell L1E may be changed bychanging the size of the pixel region L1Ea containing a pixel 51A andthus the size of the reflection surface 51S of the pixel 51A. Inaddition, it is possible to increase the range of tones in the image Pdisplayed by the display body 50 since the intensity of light per areahaving the same size as a unit cell L1E can be changed by changing thesize of the reflection surface 51S.

As shown in FIG. 29, the area of the reflection surface 51S according tothe azimuth angle Φ, in other words, the size of the pixel region L1Eaaccording to the azimuth angle Φ, may be set using an ellipse having aradius that varies continuously with the azimuth angle Φ. In the ellipseshown in FIG. 29, each arrow AR represents the projection direction DPof a reflection surface 51S. The length of the arrow AR extending to theellipse is proportional to the size of the pixel region L1Ea. The sizeof the pixel region L1Ea of each unit cell L1E is set accordingly.

The ratio of the diameter in the X direction and the diameter in the Ydirection of the ellipse may be appropriately changed when the size ofthe pixel region L1Ea is changed corresponding to a change in theazimuth angle Φ per unit angle.

As described above, when the display body 50 is observed from the firstobservation side such that the inclination angle Θ between the displaysurface 50S and the horizontal plane HR is 45° and the plane includingthe observation direction is perpendicular to the display surface 50S, areflection surface 51S with an azimuth angle Φ of 180° provides thehighest brightness, and the greater the difference between 180° and anazimuth angle Φ, the lower the brightness of the reflection surface 51S.This observation state is referred to as the first observation state.

In contrast, when the display body 50 is tilted from this state in thefront-back direction, a reflection surface 51S with an azimuth angle Φof 0° provides the highest brightness, and the greater the differencebetween 0° and an azimuth angle Φ, the lower the brightness of thereflection surface 51S. Specifically, the observer OB tilts the displaybody 50 such that the section of the display surface 50S of the displaybody 50 that intersects with the plane including the observationdirection and extending along the X direction and the section of theplane including the observation direction that intersects with thedisplay surface 50S remain unchanged. The state of the display body 50thus tilted is referred to as the second observation state.

Switching the observation state of the display body 50 between the firstobservation state and the second observation state significantly changesthe intensities of the light that is perceived by the observer OB andreflected from the reflection surfaces 51S having azimuth angles Φ ofaround 0° and the reflection surfaces 51S having azimuth angles Φ ofaround 180°. In contrast, the intensities of the light reflected fromthe reflection surfaces 51S having azimuth angles Φ of around 90° andperceived by the observer OB do not significantly change when theobservation state of the display body 50 is switched between the firstobservation state and the second observation state.

Thus, while the observation state of the display body 50 is switchedbetween the first observation state and the second observation state,the reflection surfaces 51S that display the first image and haveazimuth angles Φ of around 90° and the reflection surfaces 51S thatdisplay the second image and have azimuth angles Φ of around 90° becomeequivalent in brightness. As such, the images displayed by thesereflection surfaces 51S tend to be perceived as one image.

In this respect, according to the ellipse shown in FIG. 29, an azimuthangle closer to 90° results in a smaller pixel region L1Ea, reducing theamount of light emerged by a reflection surface 51S having an azimuthangle of around 90°. This lowers the visibility of the light emergedfrom reflection surfaces 51S with azimuth angles of around 90°, so thatthe image displayed by reflection surfaces 51S for displaying the firstimage and the image displayed by reflection surfaces 51S for displayingthe second image are less likely to be perceived as one image. As aresult, the visibility of the display body 50 is improved.

Further, in the first and second images, the pixel regions L1Ea forrepresenting sections with lower lightness are smaller in size than thepixel regions L1Ea for representing sections with higher lightness. Thisincreases the contrast in each image as compared with a configuration inwhich the pixels 51A have pixel regions L1Ea of the same size.

OTHER EMBODIMENTS

The above-described embodiments may be modified as follows.

In each of the embodiments described above, when the pixels 11A, 21A and31A are made of a material with light reflectivity, the reflectionlayers may be omitted. Exposed surfaces of the pixels 11A, 21A and 31Amay function as reflection surfaces.

In the first embodiment, when the direction in which the display body 10is observed is varied, the element images in the image are identical intype but differ from one another in shape according to the reflectiondirection. In the second embodiment, when the direction in which thedisplay body 20 is observed is changed, the element images in the imageare identical in type but differ from one another in position accordingto the reflection direction.

In the fourth embodiment, when the direction in which the display body40 is observed is changed, the element images in the image are identicalin type but differ from one another in shade according to the reflectiondirection. Alternatively, when the direction in which the display body10, 20 or 40 is observed is changed, the element images in the image maybe identical in type but differ from one another in size or brightnessaccording to the reflection direction. Further, when the direction inwhich the display body 10, 20 or 40 is observed is changed, the elementimages in the image may be identical in type but differ from one anotherin a combination of position, shape, size, light and dark, and shade,which function as control parameters.

In other words, the display body may have any configuration providedthat different images corresponding to the directions in which thedisplay body is observed each include an element image, and the elementimages are identical in type and differ from one another in at least oneof position, shape, size, light and dark, and shade.

In each of the embodiments, the orientation of the reflection surface11S of each pixel 11A (21A, 31A) is modified to adjust the direction oflight diffracted by the pixel 11A (21A, 31A). Alternatively or inaddition to this, as shown in FIGS. 30A to 30D, the direction ofdiffracted light from each pixel 11A (21A, 31A) may be adjusted byadjusting the length in the X direction of the reflection surface 11S ofthe pixel 11A as a pitch D1 to D4 of the reflection surface 11S of thepixel 11A, while maintaining its height H. The pitch is equal to thestructure width described above. With respect to the pixel 11A (21A,31A) shown in FIG. 30A, the pixels 11A (21A, 31A) of FIGS. 30B to 30Dare arranged in ascending order of degree of adjustment in pitch of thereflection surface 11S.

FIGS. 31A to 31D are cross-sectional views of the pixels 11A (21A, 31A)of FIGS. 30A to 30D in the X direction. FIG. 31A is a cross-sectionalview corresponding to the pixel 11A (21A, 31A) shown in FIG. 30A, andFIG. 31B is a cross-sectional view corresponding to the pixel 11A (21A,31A) shown in FIG. 30B. FIG. 31C is a cross-sectional view correspondingto the pixel 11A (21A, 31A) shown in FIG. 30C, and FIG. 31D is across-sectional view corresponding to the pixel 11A (21A, 31A) shown inFIG. 30D. In this example, the reflection surfaces 11S of these fourtypes of pixels 11A (21A, 31A) have the same height H. As the pitch ofthe reflection surface 11S of the pixel 11A (21A and 31A) increases fromD1 to D4, the inclination angle formed by the reflection surface 11S andthe display surface 10S in the pixel 11A (21A, 31A) gradually decreasesfrom θ1′ to θ4′.

That is, there is a certain interrelation between the pitches D1 to D4of the reflection surfaces 11S of the pixels 11A and the inclinationangles θ1′ to θ4′ of the reflection surfaces 11S of the pixels 11A incross sections perpendicular to the display surface 10S. The differentpitches D1 to D4 of the reflection surfaces 11S of the pixels 11A resultin the different inclination angles θ1′ to θ4′ of the reflectionsurfaces 11S of the pixels 11A in the cross sections. The followingadvantage is achieved by adjusting pitches D1 to D4 of the reflectionsurfaces 11S of pixels 11A (21A, 31A), instead of or in addition to theorientation of the reflection surface 11S of each pixel 11A (21A, 31A).That is, in cross sections perpendicular to the display surface 10S, itis possible to have a wider variety of inclination angles θ1′ to θ4′ ofthe reflection surfaces 11S of pixels 11A (21A, 31A). In other words,the inclination angles θ of the reflection surfaces 11S may be set to agreater range of values. This configuration allows the display body 10to display an image with multilayered gradations.

Similarly, as shown in FIGS. 32A to 32D, the height H1 to H4 of thereflection surface 11S of each pixel 11A (21A, 31A) may be adjusted,while maintaining the pitch D of the reflection surface 11S of eachpixel 11A (21A, 31A). With respect to the pixel 11A (21A, 31A) shown inFIG. 32A, the pixels 11A (21A, 31A) of FIGS. 32B to 32D are arranged inascending order of degree of adjustment in height of the reflectionsurface 11S.

FIGS. 33A to 33D are cross-sectional views of the pixels 11A (21A, 31A)of FIGS. 32A to 32D in the X direction. FIG. 33A is a cross-sectionalview corresponding to the pixel 11A (21A, 31A) shown in FIG. 32A, andFIG. 33B is a cross-sectional view corresponding to the pixel 11A (21A,31A) shown in FIG. 32B. FIG. 33C is a cross-sectional view correspondingto the pixel 11A (21A, 31A) shown in FIG. 32C, and FIG. 33D is across-sectional view corresponding to the pixel 11A (21A, 31A) shown inFIG. 32D. In this example, the four types of pixels 11A (21A, 31A) havethe same pitch D. Thus, as the height of the reflection surface 11S ofthe pixel 11A (21A and 31A) decreases from H1 to H4, the inclinationangle formed by the reflection surface 11S and the display surface 10Sin the pixel 11A (21A, 31A) gradually decreases from θ1″ to θ4″.

That is, there is a certain interrelation between the heights H1 to H4of the reflection surfaces 11S of the pixels 11A (21A, 31A) and theinclination angles θ1″ to θ4″ of the reflection surfaces 11S of thepixels 11A (21A, 31A) in cross sections perpendicular to the displaysurface 10S. The different heights H1 to H4 of the reflection surfaces11S of the pixels 11A (21A, 31A) result in the different inclinationangles θ1″ to θ4″ of the reflection surfaces 11S of the pixels 11A (21A,31A) in the cross sections. The following advantage is achieved byadjusting heights H1 to H4 of the reflection surfaces 11S of pixels 11A(21A, 31A), instead of or in addition to the orientation of thereflection surface 11S of each pixel 11A (21A, 31A). That is, in crosssections perpendicular to the display surface 10S, it is possible tohave a wider variety of inclination angles θ of the reflection surfaces11S of the pixels 11A (21A, 31A). In other words, the inclination anglesθ of the reflection surfaces 11S may be set to a greater range ofvalues. This configuration allows the display body 10 to display animage with multilayered gradations.

In the embodiments described above, the reflection directions of thedisplay region groups of the display body 10, 20, 30 or 40 varycontinuously, so that the images formed in the reflection directionsvary continuously. However, continuous varies of the image according tothe reflection direction of the display body 10, 20, 30 or 40 are notnecessarily required. The image may vary intermittently according to thesequence of reflection directions of the display body 10, 20, 30 or 40.For example, a motionless image may repeatedly appear and disappear. Inother words, the display body may have any configuration as long asthere is a certain interrelation between the images that are formed intwo adjacent reflection directions among various reflection directions.

In this configuration, as described above with reference to FIGS. 15 to16B, both of the first image P1 displayed by the first region group AS1and the second image P2 displayed by the second region group AS2 may beperceived as two-dimensional images, and the image displayed may beswitched between these two images. Further, in a configuration thatswitches the image to be displayed between two images, at least one ofthe first image P1 and the second image P2 may be a three-dimensionalimage, such as the three-dimensional image described for the fourthembodiment, a modification of the fourth embodiment, or the fifthembodiment. Further, the display body may have a display surface onwhich three or more images can be displayed.

For example, when both of the first and second images P1 and P2 arethree-dimensional images, the configuration described below withreference to FIGS. 34A and 34B may be used. FIG. 34A shows an imagedisplayed by a display body 60 when the observer OB views the displaybody 60 under the conditions described above referring to FIG. 16A. FIG.34B shows an image displayed by the display body 60 when the observer OBviews the display body 60 under the conditions described above referringto FIG. 16B.

That is, as shown in FIG. 34A, the display body 60 can display athree-dimensional image as the first image P1. In this modification, thefirst image P1 represents a banana three-dimensionally, but the image P1may represent other object three-dimensionally.

On the other hand, as shown in FIG. 34B, when the observer OB views thedisplay body 60 under conditions different from those in FIG. 34A, thedisplay body 60 displays a three-dimensional image as the second imageP2, which differs from the first image P1. In this modification, thesecond image P2 represents lemons three-dimensionally, but the secondimage P2 may represent other object three-dimensionally, as long as thesecond image P2 differs from the first image P1. Alternatively, thefirst image P1 and the second image P2 may be identical images.

As described above, the range of azimuth angles Φ of the reflectionsurfaces for displaying the first image P1 differs from the range ofazimuth angles Φ of the reflection surfaces for displaying the secondimage P2. This allows the display body 60 to display the first image P1and the second image P2 individually depending on the conditions underwhich the observer OB views the display body 60. For example, the rangeof azimuth angles Φ of the reflection surfaces for displaying the firstimage P1 is between 0° to 90° inclusive, while the range of azimuthangles Φ of the reflection surfaces for displaying the second image P2is between 100° and 180° inclusive.

In this display body 60, the extent of the range of azimuth angles Φ ofthe reflection surfaces for displaying the first image P1 may bedifferent from the extent of the range of azimuth angles Φ of thereflection surfaces for displaying the second image P2, so that therange of lightness of the first image P1 differs from the range oflightness of the second image P2. For example, the extent of the rangeof azimuth angles Φ of the reflection surfaces for displaying the firstimage P1 may be set to 10°, while the extent of the range of azimuthangles Φ of the reflection surfaces for displaying the second image P2may be set to 80°. This allows the observer to easily recognizeswitching between the first image P1 and the second image P2, ascompared with a configuration in which the range of lightness of thefirst image P1 is equal to the range of lightness of the second imageP2.

For example, when the first image P1 is a two-dimensional image and thesecond image P2 is a three-dimensional image, the configurationdescribed below with reference to FIGS. 35A and 35B may be used. FIG.35A shows the image displayed by a display body 70 when the observer OBviews the display body 70 under the conditions described above referringto FIG. 16A. FIG. 35B shows the image displayed by the display body 70when the observer OB views the display body 70 under the conditionsdescribed above referring to FIG. 16B.

That is, as shown in FIG. 35A, the display body 70 displays as the firstimage P1 a two-dimensional image having a uniform lightness over theentire image. In this modification, the first image P1 displays theletters ABC, which is an example of a character string. As long as thefirst image P1 displays a two-dimensional image, the first image P1 mayhave a shape representing other characters, or may have a shaperepresenting any one of number, symbol, graphics, and illustration.

On the other hand, as shown in FIG. 35B, the display body 70 can displaya three-dimensional image as the second image P2. In this modification,the second image P2 represents lemons three-dimensionally, but thesecond image P2 may represent a three-dimensional image of anotherobject.

The display body 70 can display the two-dimensional first image P1 andthe three-dimensional second image P2. The first image P1 has a uniformlightness, so that the display body 70 can display an image that iseasier to perceive than the second image P2. The display body 70 canalso display the second image P2, achieving an improved aestheticappearance as compared with a configuration that displays only an imagewith a uniform lightness.

As with the example described above referring to FIGS. 35A and 35B inwhich the first image P1 is a character string and the second image P2is an illustration, when two images have different attributes, in otherwords, when two images belong to different categories, the observer OBeasily notices switching between the first image P1 and the second imageP2.

In each of the embodiments, each pixel 11A (21A, 31A) may have aplurality of inclined surfaces. In this case, as shown in FIG. 36A,inclined surfaces 11Sα and 11Sβ may form different inclination angles θαand θβ with the display surface 10S. Alternatively, as shown in FIG.36B, the inclination angles θα and θβ formed by the inclined surfaces11Sα and 11Sα with the display surface 10S may be equal to each other.In the example shown in FIG. 36A, the inclined surface 11Sα having thesmaller inclination angle θα functions as the reflection surface forforming an image in the reflection direction. Alternatively, theinclined surface 11Sβ having the larger inclination angle θβ mayfunction as the reflection surface for forming an image in thereflection direction. In the example shown in FIG. 36B, one of theinclined surfaces 11Sα and 11Sβ having the equal inclination angles θαand θβ functions as the reflection surface for forming an image in thereflection direction.

DESCRIPTION OF THE REFERENCE NUMERALS

10, 20, 30, 40 . . . Display body; 10S, 20S, 30S, 40S . . . Displaysurface; 11A, 21A, 31A . . . Pixel; 11S . . . Reflection surface; 11Sa,21Sa, 31Sa . . . First pixel group; 11Sb, 21Sb, 31Sb . . . Second pixelgroup; 11Sc, 21Sc, 31Sc . . . Third pixel group; 11Sd, 21Sd . . . Fourthpixel group; 11Se, 21Se . . . Fifth pixel group; L1E, L2E, L3E . . .Unit cell; P . . . Image

The invention claimed is:
 1. A display body comprising a display surface including a plurality of display region groups, each including a plurality of display regions, wherein the display surface includes a plurality of unit cells that are arranged in a first direction and in a second direction which is perpendicular to the first direction, each display region is a minimum unit in the plurality of display region groups, wherein each unit cell includes one display region, each display region includes at least one reflection surface that is configured to reflect light incident on the display surface toward an area including a corresponding one of reflection directions that are associated with the respective display region groups, at least one of the plurality of display regions has a first reflection section which has a first reflection surface of the at least one reflection surface and a second reflection section which has a second reflection surface of the at least one reflection surface, the first reflection section is different from the second reflection section in height, an inclination angle formed by the first reflection surface and the display surface is equal to an inclination angle formed by the second reflection surface and the display surface, each display region group is configured to form an image unique to the display region group in the corresponding one of the reflection directions through reflection of light on the reflection surfaces in the display region group, when a first angle formed by the first direction and a projection direction, which is a projection normal to the reflection surface onto the display surface, is 0°, a first area occupied by the display region in the unit cell is the largest, and the closer the first angle is to 90°, the smaller the first area, and the display region groups are configured to form, in two adjacent ones of the reflection directions, different images that have an interrelation between each other.
 2. The display body according to claim 1, wherein the images having the interrelation, where each includes an element image, and the element images are identical in type and different from each other in at least one of position of the element images, shape of the element images, size of the element images, light and dark of the element images, and shade of the element images.
 3. The display body according to claim 2, wherein the interrelation includes continuous variations, along a sequence of the reflection directions, in at least one of position of the element images, the shape of the element images, the light and dark of the element images, the size of the element images, and the shade of the element images in the images.
 4. The display body according to claim 1, wherein the two adjacent reflection directions are a first reflection direction and a second reflection direction, the plurality of display region groups includes a first display region group configured to form an image in the first reflection direction, and a second display region group configured to form an image in the second reflection direction, and the display regions of the first display region group are adjacent to the display regions of the second display region group.
 5. The display body according to claim 1, wherein the plurality of reflection surfaces includes reflection surfaces that form different angles with the display surface and reflection surfaces having different orientations.
 6. The display body according to claim 1, further comprising a plurality of pixels located on the display surface, wherein each display region is one of the pixels.
 7. The display body according to claim 1, further comprising: a substrate; and a reflection layer covering the substrate, wherein the reflection layer includes the reflection surfaces of the display regions. 